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	$136.72	10.575%	$151.1781	$151.18	$151.20	$151.20
Purchase #2	$65.69	11.848%	$73.473	$73.47	$73.45	$73.50
Purchase #3	$227.99	9.429%	$249.4872	$249.49	$249.50	$249.50
Purchase #4	$249.93	4.178%	$260.3721	$260.37	$260.35	$260.40
Purchase #5	$59.25	11.155%	$65.8593	$65.86	$65.85	$65.90
Purchase #6	$171.46	10.774%	$189.9331	$189.93	$189.95	$189.90
Purchase #7	$77.89	6.502%	$82.9544	$82.95	$82.95	$83.00
7 purchase totals =	$988.93		$1,073.2572	$1,073.25	$1,073.25	$1,073.40