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	$124.45	7.727%	$134.0663	$134.07	$134.05	$134.10
Purchase #2	$41.88	8.553%	$45.462	$45.46	$45.45	$45.50
Purchase #3	$177.54	3.650%	$184.0202	$184.02	$184.00	$184.00
Purchase #4	$93.67	7.705%	$100.8873	$100.89	$100.90	$100.90
Purchase #5	$46.38	6.344%	$49.3223	$49.32	$49.30	$49.30
Purchase #6	$100.52	10.857%	$111.4335	$111.43	$111.45	$111.40
Purchase #7	$150.33	5.465%	$158.5455	$158.55	$158.55	$158.50
7 purchase totals =	$734.77		$783.7371	$783.74	$783.70	$783.70