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	$61.80	8.621%	$67.1278	$67.13	$67.15	$67.10
Purchase #2	$42.53	4.596%	$44.4847	$44.48	$44.50	$44.50
Purchase #3	$55.49	6.677%	$59.1951	$59.20	$59.20	$59.20
Purchase #4	$27.66	6.459%	$29.4466	$29.45	$29.45	$29.40
Purchase #5	$35.56	8.714%	$38.6587	$38.66	$38.65	$38.70
Purchase #6	$242.33	4.606%	$253.4917	$253.49	$253.50	$253.50
Purchase #7	$230.49	8.480%	$250.0356	$250.04	$250.05	$250.00
7 purchase totals =	$695.86		$742.4402	$742.45	$742.50	$742.40