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	$184.42	11.282%	$205.2263	$205.23	$205.25	$205.20
Purchase #2	$7.48	3.312%	$7.7277	$7.73	$7.75	$7.70
Purchase #3	$19.39	7.702%	$20.8834	$20.88	$20.90	$20.90
Purchase #4	$174.25	5.496%	$183.8268	$183.83	$183.85	$183.80
Purchase #5	$219.83	8.476%	$238.4628	$238.46	$238.45	$238.50
Purchase #6	$128.96	11.762%	$144.1283	$144.13	$144.15	$144.10
Purchase #7	$165.91	11.431%	$184.8752	$184.88	$184.90	$184.90
7 purchase totals =	$900.24		$985.1305	$985.14	$985.25	$985.10