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	$194.58	8.185%	$210.5064	$210.51	$210.50	$210.50
Purchase #2	$33.39	7.583%	$35.922	$35.92	$35.90	$35.90
Purchase #3	$23.57	8.155%	$25.4921	$25.49	$25.50	$25.50
Purchase #4	$122.25	7.369%	$131.2586	$131.26	$131.25	$131.30
Purchase #5	$69.82	3.442%	$72.2232	$72.22	$72.20	$72.20
Purchase #6	$126.88	11.853%	$141.9191	$141.92	$141.90	$141.90
Purchase #7	$108.53	5.601%	$114.6088	$114.61	$114.60	$114.60
7 purchase totals =	$679.02		$731.9302	$731.93	$731.85	$731.90