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	$125.50	6.528%	$133.6926	$133.69	$133.70	$133.70
Purchase #2	$116.50	9.612%	$127.698	$127.70	$127.70	$127.70
Purchase #3	$134.76	10.635%	$149.0917	$149.09	$149.10	$149.10
Purchase #4	$132.63	6.748%	$141.5799	$141.58	$141.60	$141.60
Purchase #5	$224.94	11.849%	$251.5931	$251.59	$251.60	$251.60
Purchase #6	$187.59	6.587%	$199.9466	$199.95	$199.95	$199.90
Purchase #7	$94.46	5.348%	$99.5117	$99.51	$99.50	$99.50
7 purchase totals =	$1,016.38		$1,103.1136	$1,103.11	$1,103.15	$1,103.10