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	$244.69	11.108%	$271.8702	$271.87	$271.85	$271.90
Purchase #2	$124.64	4.668%	$130.4582	$130.46	$130.45	$130.50
Purchase #3	$80.41	3.819%	$83.4809	$83.48	$83.50	$83.50
Purchase #4	$44.39	12.108%	$49.7647	$49.76	$49.75	$49.80
Purchase #5	$143.57	6.145%	$152.3924	$152.39	$152.40	$152.40
Purchase #6	$213.55	3.741%	$221.5389	$221.54	$221.55	$221.50
Purchase #7	$141.74	7.559%	$152.4541	$152.45	$152.45	$152.50
7 purchase totals =	$992.99		$1,061.9594	$1,061.95	$1,061.95	$1,062.10