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	$182.29	9.817%	$200.1854	$200.19	$200.20	$200.20
Purchase #2	$208.88	13.144%	$236.3352	$236.34	$236.35	$236.30
Purchase #3	$36.52	3.854%	$37.9275	$37.93	$37.95	$37.90
Purchase #4	$199.89	11.169%	$222.2157	$222.22	$222.20	$222.20
Purchase #5	$82.42	9.249%	$90.043	$90.04	$90.05	$90.00
Purchase #6	$119.26	11.781%	$133.31	$133.31	$133.30	$133.30
Purchase #7	$121.75	6.858%	$130.0996	$130.10	$130.10	$130.10
7 purchase totals =	$951.01		$1,050.1164	$1,050.13	$1,050.15	$1,050.00