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	$131.28	11.328%	$146.1514	$146.15	$146.15	$146.20
Purchase #2	$208.72	13.697%	$237.3084	$237.31	$237.30	$237.30
Purchase #3	$39.77	4.787%	$41.6738	$41.67	$41.65	$41.70
Purchase #4	$155.43	3.148%	$160.3229	$160.32	$160.30	$160.30
Purchase #5	$161.73	6.497%	$172.2376	$172.24	$172.25	$172.20
Purchase #6	$203.92	13.583%	$231.6185	$231.62	$231.60	$231.60
Purchase #7	$84.72	6.792%	$90.4742	$90.47	$90.45	$90.50
7 purchase totals =	$985.57		$1,079.7868	$1,079.78	$1,079.70	$1,079.80