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	$175.48	7.199%	$188.1128	$188.11	$188.10	$188.10
Purchase #2	$66.25	5.184%	$69.6844	$69.68	$69.70	$69.70
Purchase #3	$48.61	8.713%	$52.8454	$52.85	$52.85	$52.80
Purchase #4	$214.57	13.146%	$242.7774	$242.78	$242.80	$242.80
Purchase #5	$247.89	9.267%	$270.862	$270.86	$270.85	$270.90
Purchase #6	$221.98	7.470%	$238.5619	$238.56	$238.55	$238.60
Purchase #7	$82.71	6.300%	$87.9207	$87.92	$87.90	$87.90
7 purchase totals =	$1,057.49		$1,150.7646	$1,150.76	$1,150.75	$1,150.80