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	$211.76	7.371%	$227.3688	$227.37	$227.35	$227.40
Purchase #2	$130.53	8.326%	$141.3979	$141.40	$141.40	$141.40
Purchase #3	$197.69	6.748%	$211.0301	$211.03	$211.05	$211.00
Purchase #4	$131.25	10.253%	$144.7071	$144.71	$144.70	$144.70
Purchase #5	$48.25	9.631%	$52.897	$52.90	$52.90	$52.90
Purchase #6	$116.74	12.619%	$131.4714	$131.47	$131.45	$131.50
Purchase #7	$198.73	12.366%	$223.305	$223.31	$223.30	$223.30
7 purchase totals =	$1,034.95		$1,132.1773	$1,132.19	$1,132.15	$1,132.20