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	$181.50	3.749%	$188.3044	$188.30	$188.30	$188.30
Purchase #2	$6.79	5.167%	$7.1408	$7.14	$7.15	$7.10
Purchase #3	$54.26	12.153%	$60.8542	$60.85	$60.85	$60.90
Purchase #4	$33.33	11.871%	$37.2866	$37.29	$37.30	$37.30
Purchase #5	$228.27	11.506%	$254.5347	$254.53	$254.55	$254.50
Purchase #6	$153.92	9.346%	$168.3054	$168.31	$168.30	$168.30
Purchase #7	$246.45	5.545%	$260.1157	$260.12	$260.10	$260.10
7 purchase totals =	$904.52		$976.5418	$976.54	$976.55	$976.50