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	$96.81	12.183%	$108.6044	$108.60	$108.60	$108.60
Purchase #2	$228.90	7.183%	$245.3419	$245.34	$245.35	$245.30
Purchase #3	$102.66	8.424%	$111.3081	$111.31	$111.30	$111.30
Purchase #4	$139.26	9.487%	$152.4716	$152.47	$152.45	$152.50
Purchase #5	$131.36	11.350%	$146.2694	$146.27	$146.25	$146.30
Purchase #6	$155.41	10.833%	$172.2456	$172.25	$172.25	$172.20
Purchase #7	$201.96	5.202%	$212.466	$212.47	$212.45	$212.50
7 purchase totals =	$1,056.36		$1,148.7070	$1,148.71	$1,148.65	$1,148.70