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	$191.33	13.792%	$217.7182	$217.72	$217.70	$217.70
Purchase #2	$30.33	13.473%	$34.4164	$34.42	$34.40	$34.40
Purchase #3	$205.49	6.317%	$218.4708	$218.47	$218.45	$218.50
Purchase #4	$209.29	13.787%	$238.1448	$238.14	$238.15	$238.10
Purchase #5	$71.92	12.437%	$80.8647	$80.86	$80.85	$80.90
Purchase #6	$93.46	6.136%	$99.1947	$99.19	$99.20	$99.20
Purchase #7	$63.44	6.748%	$67.7209	$67.72	$67.70	$67.70
7 purchase totals =	$865.26		$956.5305	$956.52	$956.45	$956.50