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	$78.56	9.166%	$85.7608	$85.76	$85.75	$85.80
Purchase #2	$17.59	7.469%	$18.9038	$18.90	$18.90	$18.90
Purchase #3	$70.31	7.544%	$75.6142	$75.61	$75.60	$75.60
Purchase #4	$123.34	4.644%	$129.0679	$129.07	$129.05	$129.10
Purchase #5	$68.89	4.402%	$71.9225	$71.92	$71.90	$71.90
Purchase #6	$212.48	8.182%	$229.8651	$229.87	$229.85	$229.90
Purchase #7	$130.93	10.386%	$144.5284	$144.53	$144.55	$144.50
7 purchase totals =	$702.10		$755.6627	$755.66	$755.60	$755.70