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	$168.96	11.863%	$189.0037	$189.00	$189.00	$189.00
Purchase #2	$48.83	6.692%	$52.0977	$52.10	$52.10	$52.10
Purchase #3	$66.31	8.440%	$71.9066	$71.91	$71.90	$71.90
Purchase #4	$238.50	13.579%	$270.8859	$270.89	$270.90	$270.90
Purchase #5	$96.80	7.443%	$104.0048	$104.00	$104.00	$104.00
Purchase #6	$201.43	7.231%	$215.9954	$216.00	$216.00	$216.00
Purchase #7	$219.56	3.477%	$227.1941	$227.19	$227.20	$227.20
7 purchase totals =	$1,040.39		$1,131.0882	$1,131.09	$1,131.10	$1,131.10