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	$93.75	10.345%	$103.4484	$103.45	$103.45	$103.40
Purchase #2	$174.64	13.237%	$197.7571	$197.76	$197.75	$197.80
Purchase #3	$115.78	11.364%	$128.9372	$128.94	$128.95	$128.90
Purchase #4	$88.90	7.620%	$95.6742	$95.67	$95.65	$95.70
Purchase #5	$54.64	8.222%	$59.1325	$59.13	$59.15	$59.10
Purchase #6	$37.60	5.736%	$39.7567	$39.76	$39.75	$39.80
Purchase #7	$154.27	4.656%	$161.4528	$161.45	$161.45	$161.50
7 purchase totals =	$719.58		$786.1589	$786.16	$786.15	$786.20