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	$200.64	4.747%	$210.1644	$210.16	$210.15	$210.20
Purchase #2	$159.29	5.679%	$168.3361	$168.34	$168.35	$168.30
Purchase #3	$234.26	11.804%	$261.9121	$261.91	$261.90	$261.90
Purchase #4	$85.54	5.358%	$90.1232	$90.12	$90.10	$90.10
Purchase #5	$226.60	7.640%	$243.9122	$243.91	$243.90	$243.90
Purchase #6	$39.45	3.168%	$40.6998	$40.70	$40.70	$40.70
Purchase #7	$135.81	12.375%	$152.6165	$152.62	$152.60	$152.60
7 purchase totals =	$1,081.59		$1,167.7643	$1,167.76	$1,167.70	$1,167.70