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	$201.90	9.266%	$220.6081	$220.61	$220.60	$220.60
Purchase #2	$180.70	13.187%	$204.5289	$204.53	$204.55	$204.50
Purchase #3	$6.56	13.430%	$7.441	$7.44	$7.45	$7.40
Purchase #4	$128.36	10.393%	$141.7005	$141.70	$141.70	$141.70
Purchase #5	$81.79	10.663%	$90.5113	$90.51	$90.50	$90.50
Purchase #6	$172.46	7.509%	$185.41	$185.41	$185.40	$185.40
Purchase #7	$238.56	5.588%	$251.8907	$251.89	$251.90	$251.90
7 purchase totals =	$1,010.33		$1,102.0905	$1,102.09	$1,102.10	$1,102.00