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	$64.93	11.831%	$72.6119	$72.61	$72.60	$72.60
Purchase #2	$93.51	9.174%	$102.0886	$102.09	$102.10	$102.10
Purchase #3	$88.64	3.318%	$91.5811	$91.58	$91.60	$91.60
Purchase #4	$72.49	7.287%	$77.7723	$77.77	$77.75	$77.80
Purchase #5	$173.39	9.799%	$190.3805	$190.38	$190.40	$190.40
Purchase #6	$160.30	9.262%	$175.147	$175.15	$175.15	$175.10
Purchase #7	$110.55	12.721%	$124.6131	$124.61	$124.60	$124.60
7 purchase totals =	$763.81		$834.1945	$834.19	$834.20	$834.20