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	$53.93	4.651%	$56.4383	$56.44	$56.45	$56.40
Purchase #2	$226.91	11.538%	$253.0909	$253.09	$253.10	$253.10
Purchase #3	$146.27	5.637%	$154.5152	$154.52	$154.50	$154.50
Purchase #4	$96.82	8.804%	$105.344	$105.34	$105.35	$105.30
Purchase #5	$89.50	12.312%	$100.5192	$100.52	$100.50	$100.50
Purchase #6	$68.54	3.849%	$71.1781	$71.18	$71.20	$71.20
Purchase #7	$189.29	7.543%	$203.5681	$203.57	$203.55	$203.60
7 purchase totals =	$871.26		$944.6538	$944.66	$944.65	$944.60