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	$54.65	7.281%	$58.6291	$58.63	$58.65	$58.60
Purchase #2	$56.39	11.518%	$62.885	$62.89	$62.90	$62.90
Purchase #3	$73.26	6.138%	$77.7567	$77.76	$77.75	$77.80
Purchase #4	$82.29	10.230%	$90.7083	$90.71	$90.70	$90.70
Purchase #5	$185.72	8.202%	$200.9528	$200.95	$200.95	$201.00
Purchase #6	$59.56	3.854%	$61.8554	$61.86	$61.85	$61.90
Purchase #7	$37.65	5.316%	$39.6515	$39.65	$39.65	$39.70
7 purchase totals =	$549.52		$592.4388	$592.45	$592.45	$592.60