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	$190.34	11.701%	$212.6117	$212.61	$212.60	$212.60
Purchase #2	$125.62	10.169%	$138.3943	$138.39	$138.40	$138.40
Purchase #3	$230.95	8.320%	$250.165	$250.17	$250.15	$250.20
Purchase #4	$53.63	10.697%	$59.3668	$59.37	$59.35	$59.40
Purchase #5	$231.61	7.422%	$248.8001	$248.80	$248.80	$248.80
Purchase #6	$25.89	4.676%	$27.1006	$27.10	$27.10	$27.10
Purchase #7	$144.55	10.704%	$160.0226	$160.02	$160.00	$160.00
7 purchase totals =	$1,002.59		$1,096.4611	$1,096.46	$1,096.40	$1,096.50