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	$216.27	11.869%	$241.9391	$241.94	$241.95	$241.90
Purchase #2	$103.93	6.377%	$110.5576	$110.56	$110.55	$110.60
Purchase #3	$68.92	13.374%	$78.1374	$78.14	$78.15	$78.10
Purchase #4	$212.77	4.591%	$222.5383	$222.54	$222.55	$222.50
Purchase #5	$27.37	4.222%	$28.5256	$28.53	$28.55	$28.50
Purchase #6	$211.83	8.612%	$230.0728	$230.07	$230.05	$230.10
Purchase #7	$124.80	11.492%	$139.142	$139.14	$139.15	$139.10
7 purchase totals =	$965.89		$1,050.9128	$1,050.92	$1,050.95	$1,050.80