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	$69.93	3.836%	$72.6125	$72.61	$72.60	$72.60
Purchase #2	$96.30	4.741%	$100.8656	$100.87	$100.85	$100.90
Purchase #3	$196.79	13.766%	$223.8801	$223.88	$223.90	$223.90
Purchase #4	$160.75	7.377%	$172.6085	$172.61	$172.60	$172.60
Purchase #5	$199.48	10.791%	$221.0059	$221.01	$221.00	$221.00
Purchase #6	$201.81	12.548%	$227.1331	$227.13	$227.15	$227.10
Purchase #7	$174.58	8.633%	$189.6515	$189.65	$189.65	$189.70
7 purchase totals =	$1,099.64		$1,207.7572	$1,207.76	$1,207.75	$1,207.80