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	$143.86	5.693%	$152.0499	$152.05	$152.05	$152.00
Purchase #2	$140.27	11.622%	$156.5722	$156.57	$156.55	$156.60
Purchase #3	$138.39	7.380%	$148.6032	$148.60	$148.60	$148.60
Purchase #4	$241.72	11.294%	$269.0199	$269.02	$269.00	$269.00
Purchase #5	$88.87	12.633%	$100.0969	$100.10	$100.10	$100.10
Purchase #6	$225.88	8.503%	$245.0866	$245.09	$245.10	$245.10
Purchase #7	$25.86	12.217%	$29.0193	$29.02	$29.00	$29.00
7 purchase totals =	$1,004.85		$1,100.4480	$1,100.45	$1,100.40	$1,100.40