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	$141.67	5.490%	$149.4477	$149.45	$149.45	$149.40
Purchase #2	$145.63	6.750%	$155.46	$155.46	$155.45	$155.50
Purchase #3	$41.40	12.697%	$46.6566	$46.66	$46.65	$46.70
Purchase #4	$7.59	11.609%	$8.4711	$8.47	$8.45	$8.50
Purchase #5	$228.36	11.130%	$253.7765	$253.78	$253.80	$253.80
Purchase #6	$20.32	3.501%	$21.0314	$21.03	$21.05	$21.00
Purchase #7	$80.44	11.311%	$89.5386	$89.54	$89.55	$89.50
7 purchase totals =	$665.41		$724.3819	$724.39	$724.40	$724.40