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	$177.76	4.266%	$185.3432	$185.34	$185.35	$185.30
Purchase #2	$59.45	12.315%	$66.7713	$66.77	$66.75	$66.80
Purchase #3	$21.95	11.581%	$24.492	$24.49	$24.50	$24.50
Purchase #4	$169.42	9.556%	$185.6098	$185.61	$185.60	$185.60
Purchase #5	$189.89	12.777%	$214.1522	$214.15	$214.15	$214.20
Purchase #6	$61.74	3.735%	$64.046	$64.05	$64.05	$64.00
Purchase #7	$148.80	4.179%	$155.0184	$155.02	$155.00	$155.00
7 purchase totals =	$829.01		$895.4329	$895.43	$895.40	$895.40