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	$211.42	10.237%	$233.0631	$233.06	$233.05	$233.10
Purchase #2	$140.37	12.434%	$157.8236	$157.82	$157.80	$157.80
Purchase #3	$19.63	5.717%	$20.7522	$20.75	$20.75	$20.80
Purchase #4	$47.55	6.290%	$50.5409	$50.54	$50.55	$50.50
Purchase #5	$144.55	8.124%	$156.2932	$156.29	$156.30	$156.30
Purchase #6	$212.31	5.392%	$223.7578	$223.76	$223.75	$223.80
Purchase #7	$52.67	13.478%	$59.7689	$59.77	$59.75	$59.80
7 purchase totals =	$828.50		$901.9997	$901.99	$901.95	$902.10