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	$180.91	10.281%	$199.5094	$199.51	$199.50	$199.50
Purchase #2	$95.42	12.222%	$107.0822	$107.08	$107.10	$107.10
Purchase #3	$214.58	3.485%	$222.0581	$222.06	$222.05	$222.10
Purchase #4	$221.46	3.182%	$228.5069	$228.51	$228.50	$228.50
Purchase #5	$18.29	11.256%	$20.3487	$20.35	$20.35	$20.30
Purchase #6	$95.35	4.180%	$99.3356	$99.34	$99.35	$99.30
Purchase #7	$86.41	7.766%	$93.1206	$93.12	$93.10	$93.10
7 purchase totals =	$912.42		$969.9615	$969.97	$969.95	$969.90