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	$68.91	3.823%	$71.5444	$71.54	$71.55	$71.50
Purchase #2	$122.73	4.352%	$128.0712	$128.07	$128.05	$128.10
Purchase #3	$11.34	8.493%	$12.3031	$12.30	$12.30	$12.30
Purchase #4	$37.99	11.137%	$42.2209	$42.22	$42.20	$42.20
Purchase #5	$212.49	4.827%	$222.7469	$222.75	$222.75	$222.70
Purchase #6	$93.26	6.804%	$99.6054	$99.61	$99.60	$99.60
Purchase #7	$131.60	12.750%	$148.379	$148.38	$148.40	$148.40
7 purchase totals =	$678.32		$724.8709	$724.87	$724.85	$724.80