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	$210.78	12.219%	$236.5352	$236.54	$236.55	$236.50
Purchase #2	$66.82	7.555%	$71.8683	$71.87	$71.85	$71.90
Purchase #3	$226.39	7.384%	$243.1066	$243.11	$243.10	$243.10
Purchase #4	$6.59	4.549%	$6.8898	$6.89	$6.90	$6.90
Purchase #5	$7.36	4.179%	$7.6676	$7.67	$7.65	$7.70
Purchase #6	$196.50	11.185%	$218.4785	$218.48	$218.50	$218.50
Purchase #7	$147.71	7.845%	$159.2978	$159.30	$159.30	$159.30
7 purchase totals =	$862.15		$943.8438	$943.86	$943.85	$943.90