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	$44.86	3.679%	$46.5104	$46.51	$46.50	$46.50
Purchase #2	$41.83	11.562%	$46.6664	$46.67	$46.65	$46.70
Purchase #3	$40.32	5.278%	$42.4481	$42.45	$42.45	$42.40
Purchase #4	$209.81	6.682%	$223.8295	$223.83	$223.85	$223.80
Purchase #5	$77.33	5.596%	$81.6574	$81.66	$81.65	$81.70
Purchase #6	$38.83	12.776%	$43.7909	$43.79	$43.80	$43.80
Purchase #7	$40.84	5.775%	$43.1985	$43.20	$43.20	$43.20
7 purchase totals =	$493.82		$528.1012	$528.11	$528.10	$528.10