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	$130.81	3.118%	$134.8887	$134.89	$134.90	$134.90
Purchase #2	$120.34	10.774%	$133.3054	$133.31	$133.30	$133.30
Purchase #3	$105.96	7.136%	$113.5213	$113.52	$113.50	$113.50
Purchase #4	$234.47	12.776%	$264.4259	$264.43	$264.45	$264.40
Purchase #5	$64.72	12.671%	$72.9207	$72.92	$72.90	$72.90
Purchase #6	$50.45	6.176%	$53.5658	$53.57	$53.55	$53.60
Purchase #7	$227.79	8.449%	$247.036	$247.04	$247.05	$247.00
7 purchase totals =	$934.54		$1,019.6638	$1,019.68	$1,019.65	$1,019.60