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	$43.48	6.446%	$46.2827	$46.28	$46.30	$46.30
Purchase #2	$200.28	7.831%	$215.9639	$215.96	$215.95	$216.00
Purchase #3	$64.79	12.108%	$72.6348	$72.63	$72.65	$72.60
Purchase #4	$165.30	6.406%	$175.8891	$175.89	$175.90	$175.90
Purchase #5	$155.66	11.334%	$173.3025	$173.30	$173.30	$173.30
Purchase #6	$247.58	7.420%	$265.9504	$265.95	$265.95	$266.00
Purchase #7	$11.75	5.488%	$12.3948	$12.39	$12.40	$12.40
7 purchase totals =	$888.84		$962.4182	$962.40	$962.45	$962.50