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	$63.54	3.328%	$65.6546	$65.65	$65.65	$65.70
Purchase #2	$160.43	7.601%	$172.6243	$172.62	$172.60	$172.60
Purchase #3	$78.36	12.748%	$88.3493	$88.35	$88.35	$88.30
Purchase #4	$37.34	5.121%	$39.2522	$39.25	$39.25	$39.30
Purchase #5	$137.94	13.147%	$156.075	$156.08	$156.10	$156.10
Purchase #6	$168.76	13.205%	$191.0448	$191.04	$191.05	$191.00
Purchase #7	$42.51	10.123%	$46.8133	$46.81	$46.80	$46.80
7 purchase totals =	$688.88		$759.8135	$759.80	$759.80	$759.80