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	$58.57	5.274%	$61.659	$61.66	$61.65	$61.70
Purchase #2	$81.84	4.155%	$85.2405	$85.24	$85.25	$85.20
Purchase #3	$166.29	3.125%	$171.4866	$171.49	$171.50	$171.50
Purchase #4	$130.49	12.373%	$146.6355	$146.64	$146.65	$146.60
Purchase #5	$155.67	11.432%	$173.4662	$173.47	$173.45	$173.50
Purchase #6	$79.83	4.574%	$83.4814	$83.48	$83.50	$83.50
Purchase #7	$62.62	5.134%	$65.8349	$65.83	$65.85	$65.80
7 purchase totals =	$735.31		$787.8041	$787.81	$787.85	$787.80