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	$82.60	12.778%	$93.1546	$93.15	$93.15	$93.20
Purchase #2	$143.83	5.486%	$151.7205	$151.72	$151.70	$151.70
Purchase #3	$205.60	6.267%	$218.485	$218.49	$218.50	$218.50
Purchase #4	$235.82	8.268%	$255.3176	$255.32	$255.30	$255.30
Purchase #5	$224.67	11.686%	$250.9249	$250.92	$250.90	$250.90
Purchase #6	$51.90	10.656%	$57.4305	$57.43	$57.45	$57.40
Purchase #7	$173.92	12.771%	$196.1313	$196.13	$196.15	$196.10
7 purchase totals =	$1,118.34		$1,223.1644	$1,223.16	$1,223.15	$1,223.10