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	$158.71	13.314%	$179.8406	$179.84	$179.85	$179.80
Purchase #2	$165.51	11.583%	$184.681	$184.68	$184.70	$184.70
Purchase #3	$210.90	5.464%	$222.4236	$222.42	$222.40	$222.40
Purchase #4	$216.28	6.132%	$229.5423	$229.54	$229.55	$229.50
Purchase #5	$55.72	10.580%	$61.6152	$61.62	$61.60	$61.60
Purchase #6	$218.33	3.389%	$225.7292	$225.73	$225.75	$225.70
Purchase #7	$233.42	12.545%	$262.7025	$262.70	$262.70	$262.70
7 purchase totals =	$1,258.87		$1,366.5344	$1,366.53	$1,366.55	$1,366.40