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	$233.62	4.806%	$244.8478	$244.85	$244.85	$244.80
Purchase #2	$201.64	3.219%	$208.1308	$208.13	$208.15	$208.10
Purchase #3	$143.83	10.825%	$159.3996	$159.40	$159.40	$159.40
Purchase #4	$114.65	11.434%	$127.7591	$127.76	$127.75	$127.80
Purchase #5	$170.86	5.431%	$180.1394	$180.14	$180.15	$180.10
Purchase #6	$211.33	7.362%	$226.8881	$226.89	$226.90	$226.90
Purchase #7	$172.61	11.154%	$191.8629	$191.86	$191.85	$191.90
7 purchase totals =	$1,248.54		$1,339.0277	$1,339.03	$1,339.05	$1,339.00