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	$29.66	13.779%	$33.7469	$33.75	$33.75	$33.70
Purchase #2	$224.50	7.273%	$240.8279	$240.83	$240.85	$240.80
Purchase #3	$113.92	8.554%	$123.6647	$123.66	$123.65	$123.70
Purchase #4	$64.52	4.428%	$67.3769	$67.38	$67.40	$67.40
Purchase #5	$19.68	11.852%	$22.0125	$22.01	$22.00	$22.00
Purchase #6	$191.87	4.563%	$200.625	$200.63	$200.65	$200.60
Purchase #7	$250.47	12.381%	$281.4807	$281.48	$281.50	$281.50
7 purchase totals =	$894.62		$969.7346	$969.74	$969.80	$969.70