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	$134.62	3.573%	$139.43	$139.43	$139.45	$139.40
Purchase #2	$154.90	10.574%	$171.2791	$171.28	$171.30	$171.30
Purchase #3	$139.55	5.159%	$146.7494	$146.75	$146.75	$146.70
Purchase #4	$128.53	8.401%	$139.3278	$139.33	$139.35	$139.30
Purchase #5	$68.72	4.278%	$71.6598	$71.66	$71.65	$71.70
Purchase #6	$228.68	8.159%	$247.338	$247.34	$247.35	$247.30
Purchase #7	$94.51	13.319%	$107.0978	$107.10	$107.10	$107.10
7 purchase totals =	$949.51		$1,022.8819	$1,022.89	$1,022.95	$1,022.80