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	$57.80	6.665%	$61.6524	$61.65	$61.65	$61.70
Purchase #2	$52.64	4.654%	$55.0899	$55.09	$55.10	$55.10
Purchase #3	$211.80	5.135%	$222.6759	$222.68	$222.70	$222.70
Purchase #4	$250.79	5.293%	$264.0643	$264.06	$264.05	$264.10
Purchase #5	$74.59	5.418%	$78.6313	$78.63	$78.65	$78.60
Purchase #6	$151.73	7.142%	$162.5666	$162.57	$162.55	$162.60
Purchase #7	$75.59	8.181%	$81.774	$81.77	$81.75	$81.80
7 purchase totals =	$874.94		$926.4544	$926.45	$926.45	$926.60