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	$135.92	12.521%	$152.9385	$152.94	$152.95	$152.90
Purchase #2	$57.82	3.681%	$59.9484	$59.95	$59.95	$59.90
Purchase #3	$193.87	9.208%	$211.7215	$211.72	$211.70	$211.70
Purchase #4	$12.85	9.655%	$14.0907	$14.09	$14.10	$14.10
Purchase #5	$190.70	4.636%	$199.5409	$199.54	$199.55	$199.50
Purchase #6	$66.51	9.573%	$72.877	$72.88	$72.90	$72.90
Purchase #7	$7.63	9.753%	$8.3742	$8.37	$8.35	$8.40
7 purchase totals =	$665.30		$719.4912	$719.49	$719.50	$719.40