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	$135.39	4.428%	$141.3851	$141.39	$141.40	$141.40
Purchase #2	$186.78	10.700%	$206.7655	$206.77	$206.75	$206.80
Purchase #3	$63.72	13.386%	$72.2496	$72.25	$72.25	$72.20
Purchase #4	$143.71	8.378%	$155.75	$155.75	$155.75	$155.80
Purchase #5	$247.62	4.777%	$259.4488	$259.45	$259.45	$259.40
Purchase #6	$183.69	11.706%	$205.1928	$205.19	$205.20	$205.20
Purchase #7	$98.29	7.184%	$105.3512	$105.35	$105.35	$105.40
7 purchase totals =	$1,059.20		$1,146.1430	$1,146.15	$1,146.15	$1,146.20