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	$209.83	11.112%	$233.1463	$233.15	$233.15	$233.10
Purchase #2	$208.47	9.183%	$227.6138	$227.61	$227.60	$227.60
Purchase #3	$164.40	8.412%	$178.2293	$178.23	$178.25	$178.20
Purchase #4	$88.61	13.803%	$100.8408	$100.84	$100.85	$100.80
Purchase #5	$223.81	9.113%	$244.2058	$244.21	$244.20	$244.20
Purchase #6	$137.85	11.784%	$154.0942	$154.09	$154.10	$154.10
Purchase #7	$30.95	5.253%	$32.5758	$32.58	$32.60	$32.60
7 purchase totals =	$1,063.92		$1,170.7060	$1,170.71	$1,170.75	$1,170.60