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	$84.74	13.776%	$96.4138	$96.41	$96.40	$96.40
Purchase #2	$24.49	9.341%	$26.7776	$26.78	$26.80	$26.80
Purchase #3	$130.37	4.625%	$136.3996	$136.40	$136.40	$136.40
Purchase #4	$247.53	3.363%	$255.8544	$255.85	$255.85	$255.90
Purchase #5	$209.96	13.673%	$238.6678	$238.67	$238.65	$238.70
Purchase #6	$242.57	5.457%	$255.807	$255.81	$255.80	$255.80
Purchase #7	$49.45	10.325%	$54.5557	$54.56	$54.55	$54.60
7 purchase totals =	$989.11		$1,064.4759	$1,064.48	$1,064.45	$1,064.60