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	$146.78	8.253%	$158.8938	$158.89	$158.90	$158.90
Purchase #2	$207.92	5.567%	$219.4949	$219.49	$219.50	$219.50
Purchase #3	$217.70	12.362%	$244.6121	$244.61	$244.60	$244.60
Purchase #4	$165.92	9.705%	$182.0225	$182.02	$182.00	$182.00
Purchase #5	$57.95	3.503%	$59.98	$59.98	$60.00	$60.00
Purchase #6	$158.30	4.527%	$165.4662	$165.47	$165.45	$165.50
Purchase #7	$77.61	6.304%	$82.5025	$82.50	$82.50	$82.50
7 purchase totals =	$1,032.18		$1,112.9720	$1,112.96	$1,112.95	$1,113.00