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	$76.78	5.442%	$80.9584	$80.96	$80.95	$81.00
Purchase #2	$247.90	10.306%	$273.4486	$273.45	$273.45	$273.40
Purchase #3	$77.43	13.561%	$87.9303	$87.93	$87.95	$87.90
Purchase #4	$234.51	7.736%	$252.6517	$252.65	$252.65	$252.70
Purchase #5	$112.33	13.624%	$127.6338	$127.63	$127.65	$127.60
Purchase #6	$184.88	13.229%	$209.3378	$209.34	$209.35	$209.30
Purchase #7	$175.95	11.715%	$196.5625	$196.56	$196.55	$196.60
7 purchase totals =	$1,109.78		$1,228.5231	$1,228.52	$1,228.55	$1,228.50