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	$231.68	8.532%	$251.4469	$251.45	$251.45	$251.40
Purchase #2	$76.81	7.602%	$82.6491	$82.65	$82.65	$82.60
Purchase #3	$153.87	11.159%	$171.0404	$171.04	$171.05	$171.00
Purchase #4	$208.52	5.228%	$219.4214	$219.42	$219.40	$219.40
Purchase #5	$122.86	13.770%	$139.7778	$139.78	$139.80	$139.80
Purchase #6	$229.67	3.723%	$238.2206	$238.22	$238.20	$238.20
Purchase #7	$38.44	9.592%	$42.1272	$42.13	$42.15	$42.10
7 purchase totals =	$1,061.85		$1,144.6834	$1,144.69	$1,144.70	$1,144.50