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	$87.58	5.259%	$92.1858	$92.19	$92.20	$92.20
Purchase #2	$15.46	13.418%	$17.5344	$17.53	$17.55	$17.50
Purchase #3	$197.85	9.368%	$216.3846	$216.38	$216.40	$216.40
Purchase #4	$135.48	11.812%	$151.4829	$151.48	$151.50	$151.50
Purchase #5	$244.78	10.530%	$270.5553	$270.56	$270.55	$270.60
Purchase #6	$173.41	13.405%	$196.6556	$196.66	$196.65	$196.70
Purchase #7	$109.29	3.184%	$112.7698	$112.77	$112.75	$112.80
7 purchase totals =	$963.85		$1,057.5684	$1,057.57	$1,057.60	$1,057.70