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	$177.33	10.621%	$196.1642	$196.16	$196.15	$196.20
Purchase #2	$68.53	12.699%	$77.2326	$77.23	$77.25	$77.20
Purchase #3	$30.65	6.719%	$32.7094	$32.71	$32.70	$32.70
Purchase #4	$95.40	4.414%	$99.611	$99.61	$99.60	$99.60
Purchase #5	$118.47	11.321%	$131.882	$131.88	$131.90	$131.90
Purchase #6	$67.47	11.192%	$75.0212	$75.02	$75.00	$75.00
Purchase #7	$70.43	3.402%	$72.826	$72.83	$72.85	$72.80
7 purchase totals =	$628.28		$685.4464	$685.44	$685.45	$685.40