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	$247.33	7.748%	$266.4931	$266.49	$266.50	$266.50
Purchase #2	$31.65	5.802%	$33.4863	$33.49	$33.50	$33.50
Purchase #3	$169.83	8.417%	$184.1246	$184.12	$184.10	$184.10
Purchase #4	$63.92	13.356%	$72.4572	$72.46	$72.45	$72.50
Purchase #5	$28.89	11.343%	$32.167	$32.17	$32.15	$32.20
Purchase #6	$98.51	7.115%	$105.519	$105.52	$105.50	$105.50
Purchase #7	$235.55	7.634%	$253.5319	$253.53	$253.55	$253.50
7 purchase totals =	$875.68		$947.7791	$947.78	$947.75	$947.80