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	$127.97	12.165%	$143.5376	$143.54	$143.55	$143.50
Purchase #2	$139.30	10.387%	$153.7691	$153.77	$153.75	$153.80
Purchase #3	$198.30	10.243%	$218.6119	$218.61	$218.60	$218.60
Purchase #4	$139.39	6.862%	$148.9549	$148.95	$148.95	$149.00
Purchase #5	$90.64	11.796%	$101.3319	$101.33	$101.35	$101.30
Purchase #6	$161.89	8.528%	$175.696	$175.70	$175.70	$175.70
Purchase #7	$115.65	3.283%	$119.4468	$119.45	$119.45	$119.40
7 purchase totals =	$973.14		$1,061.3482	$1,061.35	$1,061.35	$1,061.30