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	$176.52	8.167%	$190.9364	$190.94	$190.95	$190.90
Purchase #2	$205.30	11.683%	$229.2852	$229.29	$229.30	$229.30
Purchase #3	$165.91	9.628%	$181.8838	$181.88	$181.90	$181.90
Purchase #4	$180.47	13.354%	$204.57	$204.57	$204.55	$204.60
Purchase #5	$34.55	9.684%	$37.8958	$37.90	$37.90	$37.90
Purchase #6	$139.26	8.808%	$151.526	$151.53	$151.55	$151.50
Purchase #7	$139.86	7.730%	$150.6712	$150.67	$150.65	$150.70
7 purchase totals =	$1,041.87		$1,146.7684	$1,146.78	$1,146.80	$1,146.80