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	$118.91	12.180%	$133.3932	$133.39	$133.40	$133.40
Purchase #2	$160.75	11.362%	$179.0144	$179.01	$179.00	$179.00
Purchase #3	$10.30	9.861%	$11.3157	$11.32	$11.30	$11.30
Purchase #4	$37.57	4.514%	$39.2659	$39.27	$39.25	$39.30
Purchase #5	$92.33	4.394%	$96.387	$96.39	$96.40	$96.40
Purchase #6	$37.51	7.119%	$40.1803	$40.18	$40.20	$40.20
Purchase #7	$161.92	13.791%	$184.2504	$184.25	$184.25	$184.30
7 purchase totals =	$619.29		$683.8069	$683.81	$683.80	$683.90