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	$231.31	10.471%	$255.5305	$255.53	$255.55	$255.50
Purchase #2	$115.33	4.590%	$120.6236	$120.62	$120.60	$120.60
Purchase #3	$220.93	6.651%	$235.6241	$235.62	$235.60	$235.60
Purchase #4	$132.25	12.486%	$148.7627	$148.76	$148.75	$148.80
Purchase #5	$146.64	3.593%	$151.9088	$151.91	$151.90	$151.90
Purchase #6	$157.82	6.750%	$168.4729	$168.47	$168.45	$168.50
Purchase #7	$30.45	5.145%	$32.0167	$32.02	$32.00	$32.00
7 purchase totals =	$1,034.73		$1,112.9393	$1,112.93	$1,112.85	$1,112.90