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	$194.89	10.851%	$216.0375	$216.04	$216.05	$216.00
Purchase #2	$36.95	10.127%	$40.6919	$40.69	$40.70	$40.70
Purchase #3	$120.29	13.637%	$136.6939	$136.69	$136.70	$136.70
Purchase #4	$136.71	7.116%	$146.4383	$146.44	$146.45	$146.40
Purchase #5	$166.91	13.570%	$189.5597	$189.56	$189.55	$189.60
Purchase #6	$96.72	3.534%	$100.1381	$100.14	$100.15	$100.10
Purchase #7	$216.66	4.765%	$226.9838	$226.98	$227.00	$227.00
7 purchase totals =	$969.13		$1,056.5432	$1,056.54	$1,056.60	$1,056.50