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	$203.93	7.369%	$218.9576	$218.96	$218.95	$219.00
Purchase #2	$90.63	11.381%	$100.9446	$100.94	$100.95	$100.90
Purchase #3	$71.45	7.130%	$76.5444	$76.54	$76.55	$76.50
Purchase #4	$217.64	3.696%	$225.684	$225.68	$225.70	$225.70
Purchase #5	$125.94	12.350%	$141.4936	$141.49	$141.50	$141.50
Purchase #6	$73.86	3.784%	$76.6549	$76.65	$76.65	$76.70
Purchase #7	$95.69	10.334%	$105.5786	$105.58	$105.60	$105.60
7 purchase totals =	$879.14		$945.8577	$945.84	$945.90	$945.90