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	$140.47	11.536%	$156.6746	$156.67	$156.65	$156.70
Purchase #2	$135.85	11.612%	$151.6249	$151.62	$151.60	$151.60
Purchase #3	$28.82	11.381%	$32.1	$32.10	$32.10	$32.10
Purchase #4	$52.91	3.529%	$54.7772	$54.78	$54.80	$54.80
Purchase #5	$210.88	12.796%	$237.8642	$237.86	$237.85	$237.90
Purchase #6	$142.29	11.576%	$158.7615	$158.76	$158.75	$158.80
Purchase #7	$17.45	8.490%	$18.9315	$18.93	$18.95	$18.90
7 purchase totals =	$728.67		$810.7339	$810.72	$810.70	$810.80