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	$140.85	11.281%	$156.7393	$156.74	$156.75	$156.70
Purchase #2	$109.70	13.158%	$124.1343	$124.13	$124.15	$124.10
Purchase #3	$49.72	7.760%	$53.5783	$53.58	$53.60	$53.60
Purchase #4	$72.81	10.216%	$80.2483	$80.25	$80.25	$80.20
Purchase #5	$195.52	9.600%	$214.2899	$214.29	$214.30	$214.30
Purchase #6	$247.43	11.486%	$275.8498	$275.85	$275.85	$275.80
Purchase #7	$50.60	13.704%	$57.5342	$57.53	$57.55	$57.50
7 purchase totals =	$866.63		$962.3741	$962.37	$962.45	$962.20