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	$225.37	8.767%	$245.1282	$245.13	$245.15	$245.10
Purchase #2	$209.67	6.813%	$223.9548	$223.95	$223.95	$224.00
Purchase #3	$119.55	10.324%	$131.8923	$131.89	$131.90	$131.90
Purchase #4	$152.76	5.241%	$160.7662	$160.77	$160.75	$160.80
Purchase #5	$13.97	13.741%	$15.8896	$15.89	$15.90	$15.90
Purchase #6	$206.51	10.238%	$227.6525	$227.65	$227.65	$227.70
Purchase #7	$158.90	5.320%	$167.3535	$167.35	$167.35	$167.40
7 purchase totals =	$1,086.73		$1,172.6371	$1,172.63	$1,172.65	$1,172.80