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	$174.91	11.518%	$195.0561	$195.06	$195.05	$195.10
Purchase #2	$120.86	6.300%	$128.4742	$128.47	$128.45	$128.50
Purchase #3	$38.45	5.167%	$40.4367	$40.44	$40.45	$40.40
Purchase #4	$72.55	7.738%	$78.1639	$78.16	$78.15	$78.20
Purchase #5	$50.29	12.812%	$56.7332	$56.73	$56.75	$56.70
Purchase #6	$203.99	12.801%	$230.1028	$230.10	$230.10	$230.10
Purchase #7	$68.60	4.216%	$71.4922	$71.49	$71.50	$71.50
7 purchase totals =	$729.65		$800.4591	$800.45	$800.45	$800.50