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	$151.78	4.831%	$159.1125	$159.11	$159.10	$159.10
Purchase #2	$232.53	13.637%	$264.2401	$264.24	$264.25	$264.20
Purchase #3	$195.51	12.216%	$219.3935	$219.39	$219.40	$219.40
Purchase #4	$196.34	13.390%	$222.6299	$222.63	$222.65	$222.60
Purchase #5	$204.45	3.263%	$211.1212	$211.12	$211.10	$211.10
Purchase #6	$208.87	4.588%	$218.453	$218.45	$218.45	$218.50
Purchase #7	$105.33	6.300%	$111.9658	$111.97	$111.95	$112.00
7 purchase totals =	$1,294.81		$1,406.9160	$1,406.91	$1,406.90	$1,406.90