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	$135.26	12.273%	$151.8605	$151.86	$151.85	$151.90
Purchase #2	$181.58	5.412%	$191.4071	$191.41	$191.40	$191.40
Purchase #3	$53.79	10.113%	$59.2298	$59.23	$59.25	$59.20
Purchase #4	$199.45	4.132%	$207.6913	$207.69	$207.70	$207.70
Purchase #5	$33.96	11.706%	$37.9354	$37.94	$37.95	$37.90
Purchase #6	$18.78	12.320%	$21.0937	$21.09	$21.10	$21.10
Purchase #7	$48.43	11.756%	$54.1234	$54.12	$54.10	$54.10
7 purchase totals =	$671.25		$723.3412	$723.34	$723.35	$723.30