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	$43.56	4.365%	$45.4614	$45.46	$45.45	$45.50
Purchase #2	$100.28	4.796%	$105.0894	$105.09	$105.10	$105.10
Purchase #3	$242.75	13.255%	$274.9265	$274.93	$274.95	$274.90
Purchase #4	$241.76	11.610%	$269.8283	$269.83	$269.85	$269.80
Purchase #5	$216.81	10.300%	$239.1414	$239.14	$239.15	$239.10
Purchase #6	$234.32	3.739%	$243.0812	$243.08	$243.10	$243.10
Purchase #7	$223.50	11.322%	$248.8047	$248.80	$248.80	$248.80
7 purchase totals =	$1,302.98		$1,426.3329	$1,426.33	$1,426.40	$1,426.30