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	$94.72	11.764%	$105.8629	$105.86	$105.85	$105.90
Purchase #2	$180.29	12.661%	$203.1165	$203.12	$203.10	$203.10
Purchase #3	$80.87	10.580%	$89.426	$89.43	$89.45	$89.40
Purchase #4	$202.37	3.525%	$209.5035	$209.50	$209.50	$209.50
Purchase #5	$160.71	3.155%	$165.7804	$165.78	$165.80	$165.80
Purchase #6	$71.77	4.723%	$75.1597	$75.16	$75.15	$75.20
Purchase #7	$33.34	7.521%	$35.8475	$35.85	$35.85	$35.80
7 purchase totals =	$824.07		$884.6965	$884.70	$884.70	$884.70