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	$248.69	4.152%	$259.0156	$259.02	$259.00	$259.00
Purchase #2	$181.67	13.605%	$206.3862	$206.39	$206.40	$206.40
Purchase #3	$225.52	13.238%	$255.3743	$255.37	$255.35	$255.40
Purchase #4	$195.26	13.130%	$220.8976	$220.90	$220.90	$220.90
Purchase #5	$228.29	6.397%	$242.8937	$242.89	$242.90	$242.90
Purchase #6	$79.93	11.709%	$89.289	$89.29	$89.30	$89.30
Purchase #7	$168.35	3.775%	$174.7052	$174.71	$174.70	$174.70
7 purchase totals =	$1,327.71		$1,448.5616	$1,448.57	$1,448.55	$1,448.60