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	$185.94	4.241%	$193.8257	$193.83	$193.85	$193.80
Purchase #2	$134.36	9.117%	$146.6096	$146.61	$146.60	$146.60
Purchase #3	$151.77	13.334%	$172.007	$172.01	$172.00	$172.00
Purchase #4	$245.41	11.730%	$274.1966	$274.20	$274.20	$274.20
Purchase #5	$209.40	10.127%	$230.6059	$230.61	$230.60	$230.60
Purchase #6	$82.55	9.390%	$90.3014	$90.30	$90.30	$90.30
Purchase #7	$124.89	4.549%	$130.5712	$130.57	$130.55	$130.60
7 purchase totals =	$1,134.32		$1,238.1174	$1,238.13	$1,238.10	$1,238.10