Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$43.41	4.275%	$45.2658	$45.27	$45.25	$45.30
Purchase #2	$57.96	8.208%	$62.7174	$62.72	$62.70	$62.70
Purchase #3	$224.31	4.181%	$233.6884	$233.69	$233.70	$233.70
Purchase #4	$100.40	11.582%	$112.0283	$112.03	$112.05	$112.00
Purchase #5	$115.25	4.596%	$120.5469	$120.55	$120.55	$120.50
Purchase #6	$113.33	11.200%	$126.023	$126.02	$126.00	$126.00
Purchase #7	$233.34	4.331%	$243.446	$243.45	$243.45	$243.40
7 purchase totals =	$888.00		$943.7158	$943.73	$943.70	$943.60