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	$92.84	3.620%	$96.2008	$96.20	$96.20	$96.20
Purchase #2	$69.52	11.466%	$77.4912	$77.49	$77.50	$77.50
Purchase #3	$151.34	6.865%	$161.7295	$161.73	$161.75	$161.70
Purchase #4	$173.31	6.312%	$184.2493	$184.25	$184.25	$184.20
Purchase #5	$185.51	13.117%	$209.8433	$209.84	$209.85	$209.80
Purchase #6	$173.79	13.294%	$196.8936	$196.89	$196.90	$196.90
Purchase #7	$28.58	10.162%	$31.4843	$31.48	$31.50	$31.50
7 purchase totals =	$874.89		$957.8920	$957.88	$957.95	$957.80