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	$146.76	7.720%	$158.0899	$158.09	$158.10	$158.10
Purchase #2	$214.46	12.144%	$240.504	$240.50	$240.50	$240.50
Purchase #3	$151.34	3.863%	$157.1863	$157.19	$157.20	$157.20
Purchase #4	$54.95	11.213%	$61.1115	$61.11	$61.10	$61.10
Purchase #5	$128.56	3.359%	$132.8783	$132.88	$132.90	$132.90
Purchase #6	$165.91	11.749%	$185.4028	$185.40	$185.40	$185.40
Purchase #7	$19.55	4.136%	$20.3586	$20.36	$20.35	$20.40
7 purchase totals =	$881.53		$955.5314	$955.53	$955.55	$955.60