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	$132.51	12.835%	$149.5177	$149.52	$149.50	$149.50
Purchase #2	$152.59	10.491%	$168.5982	$168.60	$168.60	$168.60
Purchase #3	$181.86	7.816%	$196.0742	$196.07	$196.05	$196.10
Purchase #4	$94.79	12.248%	$106.3999	$106.40	$106.40	$106.40
Purchase #5	$136.93	6.305%	$145.5634	$145.56	$145.55	$145.60
Purchase #6	$219.83	3.517%	$227.5614	$227.56	$227.55	$227.60
Purchase #7	$182.39	13.433%	$206.8904	$206.89	$206.90	$206.90
7 purchase totals =	$1,100.90		$1,200.6052	$1,200.60	$1,200.55	$1,200.70