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	$208.29	6.819%	$222.4933	$222.49	$222.50	$222.50
Purchase #2	$223.30	7.542%	$240.1413	$240.14	$240.15	$240.10
Purchase #3	$79.38	12.146%	$89.0215	$89.02	$89.00	$89.00
Purchase #4	$51.42	12.234%	$57.7107	$57.71	$57.70	$57.70
Purchase #5	$100.78	8.500%	$109.3463	$109.35	$109.35	$109.30
Purchase #6	$112.90	8.110%	$122.0562	$122.06	$122.05	$122.10
Purchase #7	$92.25	13.110%	$104.344	$104.34	$104.35	$104.30
7 purchase totals =	$868.32		$945.1133	$945.11	$945.10	$945.00