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	$47.98	3.732%	$49.7706	$49.77	$49.75	$49.80
Purchase #2	$200.79	11.395%	$223.67	$223.67	$223.65	$223.70
Purchase #3	$56.34	10.308%	$62.1475	$62.15	$62.15	$62.10
Purchase #4	$88.55	6.749%	$94.5262	$94.53	$94.55	$94.50
Purchase #5	$207.54	7.186%	$222.4538	$222.45	$222.45	$222.50
Purchase #6	$244.40	4.260%	$254.8114	$254.81	$254.80	$254.80
Purchase #7	$40.88	4.783%	$42.8353	$42.84	$42.85	$42.80
7 purchase totals =	$886.48		$950.2148	$950.22	$950.20	$950.20