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	$51.88	13.198%	$58.7271	$58.73	$58.75	$58.70
Purchase #2	$82.42	12.867%	$93.025	$93.03	$93.05	$93.00
Purchase #3	$144.91	6.144%	$153.8133	$153.81	$153.80	$153.80
Purchase #4	$192.42	6.561%	$205.0447	$205.04	$205.05	$205.00
Purchase #5	$157.81	6.667%	$168.3312	$168.33	$168.35	$168.30
Purchase #6	$30.69	4.483%	$32.0658	$32.07	$32.05	$32.10
Purchase #7	$196.30	13.172%	$222.1566	$222.16	$222.15	$222.20
7 purchase totals =	$856.43		$933.1637	$933.17	$933.20	$933.10