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	$33.98	8.144%	$36.7473	$36.75	$36.75	$36.70
Purchase #2	$243.53	9.703%	$267.1597	$267.16	$267.15	$267.20
Purchase #3	$70.60	11.498%	$78.7176	$78.72	$78.70	$78.70
Purchase #4	$243.28	12.537%	$273.78	$273.78	$273.80	$273.80
Purchase #5	$220.90	4.862%	$231.6402	$231.64	$231.65	$231.60
Purchase #6	$37.34	4.806%	$39.1346	$39.13	$39.15	$39.10
Purchase #7	$163.47	3.589%	$169.3369	$169.34	$169.35	$169.30
7 purchase totals =	$1,013.10		$1,096.5163	$1,096.52	$1,096.55	$1,096.40