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	$28.88	12.151%	$32.3892	$32.39	$32.40	$32.40
Purchase #2	$10.65	10.551%	$11.7737	$11.77	$11.75	$11.80
Purchase #3	$61.70	8.438%	$66.9062	$66.91	$66.90	$66.90
Purchase #4	$194.28	5.202%	$204.3864	$204.39	$204.40	$204.40
Purchase #5	$68.38	4.557%	$71.4961	$71.50	$71.50	$71.50
Purchase #6	$240.99	13.572%	$273.6972	$273.70	$273.70	$273.70
Purchase #7	$5.95	11.699%	$6.6461	$6.65	$6.65	$6.60
7 purchase totals =	$610.83		$667.2949	$667.31	$667.30	$667.30