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	$140.30	9.666%	$153.8614	$153.86	$153.85	$153.90
Purchase #2	$68.67	3.607%	$71.1469	$71.15	$71.15	$71.10
Purchase #3	$108.34	9.593%	$118.7331	$118.73	$118.75	$118.70
Purchase #4	$90.41	6.369%	$96.1682	$96.17	$96.15	$96.20
Purchase #5	$107.58	8.192%	$116.393	$116.39	$116.40	$116.40
Purchase #6	$29.95	6.342%	$31.8494	$31.85	$31.85	$31.80
Purchase #7	$159.27	9.118%	$173.7922	$173.79	$173.80	$173.80
7 purchase totals =	$704.52		$761.9442	$761.94	$761.95	$761.90