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	$150.40	8.142%	$162.6456	$162.65	$162.65	$162.60
Purchase #2	$68.31	5.491%	$72.0609	$72.06	$72.05	$72.10
Purchase #3	$95.72	10.689%	$105.9515	$105.95	$105.95	$106.00
Purchase #4	$52.47	8.788%	$57.0811	$57.08	$57.10	$57.10
Purchase #5	$39.88	8.632%	$43.3224	$43.32	$43.30	$43.30
Purchase #6	$14.74	7.844%	$15.8962	$15.90	$15.90	$15.90
Purchase #7	$55.34	10.849%	$61.3438	$61.34	$61.35	$61.30
7 purchase totals =	$476.86		$518.3015	$518.30	$518.30	$518.30