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	$221.79	11.642%	$247.6108	$247.61	$247.60	$247.60
Purchase #2	$243.27	12.667%	$274.085	$274.09	$274.10	$274.10
Purchase #3	$221.70	11.622%	$247.466	$247.47	$247.45	$247.50
Purchase #4	$72.33	5.701%	$76.4535	$76.45	$76.45	$76.50
Purchase #5	$71.77	8.510%	$77.8776	$77.88	$77.90	$77.90
Purchase #6	$146.80	12.318%	$164.8828	$164.88	$164.90	$164.90
Purchase #7	$64.79	12.196%	$72.6918	$72.69	$72.70	$72.70
7 purchase totals =	$1,042.45		$1,161.0675	$1,161.07	$1,161.10	$1,161.20