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	$156.34	11.232%	$173.9001	$173.90	$173.90	$173.90
Purchase #2	$121.74	7.620%	$131.0166	$131.02	$131.00	$131.00
Purchase #3	$30.35	11.390%	$33.8069	$33.81	$33.80	$33.80
Purchase #4	$48.64	7.430%	$52.254	$52.25	$52.25	$52.30
Purchase #5	$90.98	4.583%	$95.1496	$95.15	$95.15	$95.10
Purchase #6	$73.39	12.251%	$82.381	$82.38	$82.40	$82.40
Purchase #7	$53.79	11.744%	$60.1071	$60.11	$60.10	$60.10
7 purchase totals =	$575.23		$628.6153	$628.62	$628.60	$628.60