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	$95.83	13.591%	$108.8543	$108.85	$108.85	$108.90
Purchase #2	$40.26	4.813%	$42.1977	$42.20	$42.20	$42.20
Purchase #3	$196.57	8.499%	$213.2765	$213.28	$213.30	$213.30
Purchase #4	$170.95	6.158%	$181.4771	$181.48	$181.50	$181.50
Purchase #5	$214.60	13.598%	$243.7813	$243.78	$243.80	$243.80
Purchase #6	$6.85	9.652%	$7.5112	$7.51	$7.50	$7.50
Purchase #7	$45.51	10.151%	$50.1297	$50.13	$50.15	$50.10
7 purchase totals =	$770.57		$847.2278	$847.23	$847.30	$847.30