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	$56.36	7.296%	$60.472	$60.47	$60.45	$60.50
Purchase #2	$84.58	3.456%	$87.5031	$87.50	$87.50	$87.50
Purchase #3	$56.75	3.709%	$58.8549	$58.85	$58.85	$58.90
Purchase #4	$91.71	4.150%	$95.516	$95.52	$95.50	$95.50
Purchase #5	$48.78	12.556%	$54.9048	$54.90	$54.90	$54.90
Purchase #6	$53.56	11.491%	$59.7146	$59.71	$59.70	$59.70
Purchase #7	$176.92	6.488%	$188.3986	$188.40	$188.40	$188.40
7 purchase totals =	$568.66		$605.3640	$605.35	$605.30	$605.40