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	$225.77	5.592%	$238.3951	$238.40	$238.40	$238.40
Purchase #2	$96.90	3.485%	$100.277	$100.28	$100.30	$100.30
Purchase #3	$209.84	7.157%	$224.8582	$224.86	$224.85	$224.90
Purchase #4	$158.45	8.843%	$172.4617	$172.46	$172.45	$172.50
Purchase #5	$232.54	12.159%	$260.8145	$260.81	$260.80	$260.80
Purchase #6	$75.75	10.356%	$83.5947	$83.59	$83.60	$83.60
Purchase #7	$13.63	7.290%	$14.6236	$14.62	$14.60	$14.60
7 purchase totals =	$1,012.88		$1,095.0248	$1,095.02	$1,095.00	$1,095.10