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	$148.31	7.410%	$159.2998	$159.30	$159.30	$159.30
Purchase #2	$101.81	9.799%	$111.7864	$111.79	$111.80	$111.80
Purchase #3	$71.71	13.134%	$81.1284	$81.13	$81.15	$81.10
Purchase #4	$82.96	9.456%	$90.8047	$90.80	$90.80	$90.80
Purchase #5	$99.55	13.543%	$113.0321	$113.03	$113.05	$113.00
Purchase #6	$26.52	4.331%	$27.6686	$27.67	$27.65	$27.70
Purchase #7	$126.86	11.707%	$141.7115	$141.71	$141.70	$141.70
7 purchase totals =	$657.72		$725.4315	$725.43	$725.45	$725.40