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	$95.64	11.239%	$106.389	$106.39	$106.40	$106.40
Purchase #2	$80.65	6.399%	$85.8108	$85.81	$85.80	$85.80
Purchase #3	$180.47	11.166%	$200.6213	$200.62	$200.60	$200.60
Purchase #4	$162.55	7.125%	$174.1317	$174.13	$174.15	$174.10
Purchase #5	$125.33	5.210%	$131.8597	$131.86	$131.85	$131.90
Purchase #6	$34.53	6.334%	$36.7171	$36.72	$36.70	$36.70
Purchase #7	$194.33	5.742%	$205.4884	$205.49	$205.50	$205.50
7 purchase totals =	$873.50		$941.0180	$941.02	$941.00	$941.00