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	$112.50	13.328%	$127.494	$127.49	$127.50	$127.50
Purchase #2	$192.35	6.652%	$205.1451	$205.15	$205.15	$205.10
Purchase #3	$116.52	12.532%	$131.1223	$131.12	$131.10	$131.10
Purchase #4	$187.67	6.306%	$199.5045	$199.50	$199.50	$199.50
Purchase #5	$85.38	11.642%	$95.3199	$95.32	$95.30	$95.30
Purchase #6	$172.72	10.348%	$190.5931	$190.59	$190.60	$190.60
Purchase #7	$91.30	3.610%	$94.5959	$94.60	$94.60	$94.60
7 purchase totals =	$958.44		$1,043.7748	$1,043.77	$1,043.75	$1,043.70