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	$19.76	11.334%	$21.9996	$22.00	$22.00	$22.00
Purchase #2	$145.43	13.562%	$165.1532	$165.15	$165.15	$165.20
Purchase #3	$190.28	8.718%	$206.8686	$206.87	$206.85	$206.90
Purchase #4	$212.45	10.503%	$234.7636	$234.76	$234.75	$234.80
Purchase #5	$222.83	6.868%	$238.134	$238.13	$238.15	$238.10
Purchase #6	$136.51	6.826%	$145.8282	$145.83	$145.85	$145.80
Purchase #7	$129.29	7.788%	$139.3591	$139.36	$139.35	$139.40
7 purchase totals =	$1,056.55		$1,152.1063	$1,152.10	$1,152.10	$1,152.20