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	$223.82	4.280%	$233.3995	$233.40	$233.40	$233.40
Purchase #2	$131.33	6.585%	$139.9781	$139.98	$140.00	$140.00
Purchase #3	$127.30	3.808%	$132.1476	$132.15	$132.15	$132.10
Purchase #4	$139.40	8.810%	$151.6811	$151.68	$151.70	$151.70
Purchase #5	$119.41	10.819%	$132.329	$132.33	$132.35	$132.30
Purchase #6	$102.86	9.681%	$112.8179	$112.82	$112.80	$112.80
Purchase #7	$142.36	11.833%	$159.2055	$159.21	$159.20	$159.20
7 purchase totals =	$986.48		$1,061.5587	$1,061.57	$1,061.60	$1,061.50