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	$48.72	11.763%	$54.4509	$54.45	$54.45	$54.50
Purchase #2	$212.89	12.217%	$238.8988	$238.90	$238.90	$238.90
Purchase #3	$56.91	9.581%	$62.3625	$62.36	$62.35	$62.40
Purchase #4	$210.41	11.508%	$234.624	$234.62	$234.60	$234.60
Purchase #5	$55.37	3.550%	$57.3356	$57.34	$57.35	$57.30
Purchase #6	$244.93	10.632%	$270.971	$270.97	$270.95	$271.00
Purchase #7	$100.26	6.484%	$106.7609	$106.76	$106.75	$106.80
7 purchase totals =	$929.49		$1,025.4037	$1,025.40	$1,025.35	$1,025.50