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	$121.63	4.282%	$126.8382	$126.84	$126.85	$126.80
Purchase #2	$120.99	13.853%	$137.7507	$137.75	$137.75	$137.80
Purchase #3	$123.30	7.699%	$132.7929	$132.79	$132.80	$132.80
Purchase #4	$184.44	6.585%	$196.5854	$196.59	$196.60	$196.60
Purchase #5	$44.50	11.428%	$49.5855	$49.59	$49.60	$49.60
Purchase #6	$29.44	7.218%	$31.565	$31.57	$31.55	$31.60
Purchase #7	$37.82	11.112%	$42.0226	$42.02	$42.00	$42.00
7 purchase totals =	$662.12		$717.1403	$717.15	$717.15	$717.20