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	$84.63	4.701%	$88.6085	$88.61	$88.60	$88.60
Purchase #2	$37.82	5.407%	$39.8649	$39.86	$39.85	$39.90
Purchase #3	$244.69	7.214%	$262.3419	$262.34	$262.35	$262.30
Purchase #4	$186.45	12.252%	$209.2939	$209.29	$209.30	$209.30
Purchase #5	$200.61	8.221%	$217.1021	$217.10	$217.10	$217.10
Purchase #6	$82.89	8.814%	$90.1959	$90.20	$90.20	$90.20
Purchase #7	$184.59	13.479%	$209.4709	$209.47	$209.45	$209.50
7 purchase totals =	$1,021.68		$1,116.8781	$1,116.87	$1,116.85	$1,116.90