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	$207.54	7.285%	$222.6593	$222.66	$222.65	$222.70
Purchase #2	$230.71	4.416%	$240.8982	$240.90	$240.90	$240.90
Purchase #3	$139.33	11.791%	$155.7584	$155.76	$155.75	$155.80
Purchase #4	$134.89	12.214%	$151.3655	$151.37	$151.35	$151.40
Purchase #5	$94.95	13.102%	$107.3903	$107.39	$107.40	$107.40
Purchase #6	$217.59	4.480%	$227.338	$227.34	$227.35	$227.30
Purchase #7	$55.26	7.624%	$59.473	$59.47	$59.45	$59.50
7 purchase totals =	$1,080.27		$1,164.8827	$1,164.89	$1,164.85	$1,165.00