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	$189.31	7.108%	$202.7662	$202.77	$202.75	$202.80
Purchase #2	$225.83	9.770%	$247.8936	$247.89	$247.90	$247.90
Purchase #3	$130.94	9.309%	$143.1292	$143.13	$143.15	$143.10
Purchase #4	$131.91	12.812%	$148.8103	$148.81	$148.80	$148.80
Purchase #5	$81.68	10.819%	$90.517	$90.52	$90.50	$90.50
Purchase #6	$135.41	11.831%	$151.4304	$151.43	$151.45	$151.40
Purchase #7	$100.80	10.503%	$111.387	$111.39	$111.40	$111.40
7 purchase totals =	$995.88		$1,095.9337	$1,095.94	$1,095.95	$1,095.90