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	$25.26	3.364%	$26.1097	$26.11	$26.10	$26.10
Purchase #2	$135.57	6.593%	$144.5081	$144.51	$144.50	$144.50
Purchase #3	$86.54	11.266%	$96.2896	$96.29	$96.30	$96.30
Purchase #4	$92.66	8.542%	$100.575	$100.58	$100.60	$100.60
Purchase #5	$187.98	5.540%	$198.3941	$198.39	$198.40	$198.40
Purchase #6	$168.95	12.822%	$190.6128	$190.61	$190.60	$190.60
Purchase #7	$40.83	12.271%	$45.8402	$45.84	$45.85	$45.80
7 purchase totals =	$737.79		$802.3295	$802.33	$802.35	$802.30