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	$42.97	12.249%	$48.2334	$48.23	$48.25	$48.20
Purchase #2	$151.73	11.315%	$168.8982	$168.90	$168.90	$168.90
Purchase #3	$98.77	5.792%	$104.4908	$104.49	$104.50	$104.50
Purchase #4	$168.79	7.137%	$180.8365	$180.84	$180.85	$180.80
Purchase #5	$217.33	11.254%	$241.7883	$241.79	$241.80	$241.80
Purchase #6	$218.42	9.256%	$238.637	$238.64	$238.65	$238.60
Purchase #7	$59.44	7.854%	$64.1084	$64.11	$64.10	$64.10
7 purchase totals =	$957.45		$1,046.9926	$1,047.00	$1,047.05	$1,046.90