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	$99.30	7.688%	$106.9342	$106.93	$106.95	$106.90
Purchase #2	$122.49	11.824%	$136.9732	$136.97	$136.95	$137.00
Purchase #3	$37.48	9.781%	$41.1459	$41.15	$41.15	$41.10
Purchase #4	$86.69	8.256%	$93.8471	$93.85	$93.85	$93.80
Purchase #5	$136.82	13.546%	$155.3536	$155.35	$155.35	$155.40
Purchase #6	$63.89	13.370%	$72.4321	$72.43	$72.45	$72.40
Purchase #7	$106.69	4.402%	$111.3865	$111.39	$111.40	$111.40
7 purchase totals =	$653.36		$718.0726	$718.07	$718.10	$718.00