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	$188.33	6.384%	$200.353	$200.35	$200.35	$200.40
Purchase #2	$170.30	8.458%	$184.704	$184.70	$184.70	$184.70
Purchase #3	$61.28	6.429%	$65.2197	$65.22	$65.20	$65.20
Purchase #4	$230.48	13.598%	$261.8207	$261.82	$261.80	$261.80
Purchase #5	$129.40	6.216%	$137.4435	$137.44	$137.45	$137.40
Purchase #6	$146.85	3.158%	$151.4875	$151.49	$151.50	$151.50
Purchase #7	$129.82	10.543%	$143.5069	$143.51	$143.50	$143.50
7 purchase totals =	$1,056.46		$1,144.5353	$1,144.53	$1,144.50	$1,144.50