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	$46.89	10.155%	$51.6517	$51.65	$51.65	$51.70
Purchase #2	$130.98	7.608%	$140.945	$140.95	$140.95	$140.90
Purchase #3	$36.85	10.408%	$40.6853	$40.69	$40.70	$40.70
Purchase #4	$200.69	10.214%	$221.1885	$221.19	$221.20	$221.20
Purchase #5	$101.55	9.369%	$111.0642	$111.06	$111.05	$111.10
Purchase #6	$221.58	11.134%	$246.2507	$246.25	$246.25	$246.30
Purchase #7	$186.52	9.670%	$204.5565	$204.56	$204.55	$204.60
7 purchase totals =	$925.06		$1,016.3419	$1,016.35	$1,016.35	$1,016.50