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	$40.90	11.515%	$45.6096	$45.61	$45.60	$45.60
Purchase #2	$228.64	3.293%	$236.1691	$236.17	$236.15	$236.20
Purchase #3	$19.72	4.378%	$20.5833	$20.58	$20.60	$20.60
Purchase #4	$62.95	10.502%	$69.561	$69.56	$69.55	$69.60
Purchase #5	$181.38	13.460%	$205.7937	$205.79	$205.80	$205.80
Purchase #6	$184.77	8.258%	$200.0283	$200.03	$200.05	$200.00
Purchase #7	$98.80	13.255%	$111.8959	$111.90	$111.90	$111.90
7 purchase totals =	$817.16		$889.6409	$889.64	$889.65	$889.70