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	$106.53	6.761%	$113.7325	$113.73	$113.75	$113.70
Purchase #2	$159.49	3.759%	$165.4852	$165.49	$165.50	$165.50
Purchase #3	$150.81	9.719%	$165.4672	$165.47	$165.45	$165.50
Purchase #4	$130.75	7.760%	$140.8962	$140.90	$140.90	$140.90
Purchase #5	$190.33	12.662%	$214.4296	$214.43	$214.45	$214.40
Purchase #6	$209.67	10.464%	$231.6099	$231.61	$231.60	$231.60
Purchase #7	$57.86	11.495%	$64.511	$64.51	$64.50	$64.50
7 purchase totals =	$1,005.44		$1,096.1316	$1,096.14	$1,096.15	$1,096.10