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	$96.37	7.460%	$103.5592	$103.56	$103.55	$103.60
Purchase #2	$189.83	4.651%	$198.659	$198.66	$198.65	$198.70
Purchase #3	$248.68	10.392%	$274.5228	$274.52	$274.50	$274.50
Purchase #4	$116.57	6.218%	$123.8183	$123.82	$123.80	$123.80
Purchase #5	$32.43	9.778%	$35.601	$35.60	$35.60	$35.60
Purchase #6	$9.25	11.462%	$10.3102	$10.31	$10.30	$10.30
Purchase #7	$199.70	8.399%	$216.4728	$216.47	$216.45	$216.50
7 purchase totals =	$892.83		$962.9433	$962.94	$962.85	$963.00