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	$112.61	9.476%	$123.2809	$123.28	$123.30	$123.30
Purchase #2	$42.48	12.408%	$47.7509	$47.75	$47.75	$47.80
Purchase #3	$190.42	11.874%	$213.0305	$213.03	$213.05	$213.00
Purchase #4	$188.27	11.334%	$209.6085	$209.61	$209.60	$209.60
Purchase #5	$157.34	5.351%	$165.7593	$165.76	$165.75	$165.80
Purchase #6	$109.60	11.849%	$122.5865	$122.59	$122.60	$122.60
Purchase #7	$136.87	4.500%	$143.0292	$143.03	$143.05	$143.00
7 purchase totals =	$937.59		$1,025.0458	$1,025.05	$1,025.10	$1,025.10