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	$185.30	8.151%	$200.4038	$200.40	$200.40	$200.40
Purchase #2	$35.50	10.777%	$39.3258	$39.33	$39.35	$39.30
Purchase #3	$203.57	4.217%	$212.1545	$212.15	$212.15	$212.20
Purchase #4	$34.49	11.776%	$38.5515	$38.55	$38.55	$38.60
Purchase #5	$42.82	13.143%	$48.4478	$48.45	$48.45	$48.40
Purchase #6	$100.63	8.795%	$109.4804	$109.48	$109.50	$109.50
Purchase #7	$160.31	3.521%	$165.9545	$165.95	$165.95	$166.00
7 purchase totals =	$762.62		$814.3183	$814.31	$814.35	$814.40