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	$210.57	13.317%	$238.6116	$238.61	$238.60	$238.60
Purchase #2	$167.60	11.332%	$186.5924	$186.59	$186.60	$186.60
Purchase #3	$218.26	3.526%	$225.9558	$225.96	$225.95	$226.00
Purchase #4	$148.46	6.355%	$157.8946	$157.89	$157.90	$157.90
Purchase #5	$14.88	12.786%	$16.7826	$16.78	$16.80	$16.80
Purchase #6	$38.53	11.106%	$42.8091	$42.81	$42.80	$42.80
Purchase #7	$234.76	3.604%	$243.2208	$243.22	$243.20	$243.20
7 purchase totals =	$1,033.06		$1,111.8669	$1,111.86	$1,111.85	$1,111.90