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	$32.95	8.707%	$35.819	$35.82	$35.80	$35.80
Purchase #2	$136.61	3.561%	$141.4747	$141.47	$141.45	$141.50
Purchase #3	$87.57	13.204%	$99.1327	$99.13	$99.15	$99.10
Purchase #4	$242.36	6.577%	$258.3	$258.30	$258.30	$258.30
Purchase #5	$126.95	12.323%	$142.594	$142.59	$142.60	$142.60
Purchase #6	$191.93	3.506%	$198.6591	$198.66	$198.65	$198.70
Purchase #7	$135.35	12.433%	$152.1781	$152.18	$152.20	$152.20
7 purchase totals =	$953.72		$1,028.1576	$1,028.15	$1,028.15	$1,028.20