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	$102.39	11.708%	$114.3778	$114.38	$114.40	$114.40
Purchase #2	$94.90	11.427%	$105.7442	$105.74	$105.75	$105.70
Purchase #3	$140.54	7.244%	$150.7207	$150.72	$150.70	$150.70
Purchase #4	$143.46	8.680%	$155.9123	$155.91	$155.90	$155.90
Purchase #5	$162.65	10.547%	$179.8047	$179.80	$179.80	$179.80
Purchase #6	$234.89	5.228%	$247.17	$247.17	$247.15	$247.20
Purchase #7	$137.86	6.328%	$146.5838	$146.58	$146.60	$146.60
7 purchase totals =	$1,016.69		$1,100.3135	$1,100.30	$1,100.30	$1,100.30