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	$147.51	3.303%	$152.3823	$152.38	$152.40	$152.40
Purchase #2	$223.41	9.490%	$244.6116	$244.61	$244.60	$244.60
Purchase #3	$242.78	8.824%	$264.2029	$264.20	$264.20	$264.20
Purchase #4	$61.85	11.222%	$68.7908	$68.79	$68.80	$68.80
Purchase #5	$200.46	11.633%	$223.7795	$223.78	$223.80	$223.80
Purchase #6	$52.41	10.403%	$57.8622	$57.86	$57.85	$57.90
Purchase #7	$97.43	8.640%	$105.848	$105.85	$105.85	$105.80
7 purchase totals =	$1,025.85		$1,117.4773	$1,117.47	$1,117.50	$1,117.50