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	$14.67	9.567%	$16.0735	$16.07	$16.05	$16.10
Purchase #2	$169.60	12.182%	$190.2607	$190.26	$190.25	$190.30
Purchase #3	$33.36	12.689%	$37.5931	$37.59	$37.60	$37.60
Purchase #4	$68.59	3.540%	$71.0181	$71.02	$71.00	$71.00
Purchase #5	$31.77	6.341%	$33.7845	$33.78	$33.80	$33.80
Purchase #6	$210.72	12.789%	$237.669	$237.67	$237.65	$237.70
Purchase #7	$17.54	4.874%	$18.3949	$18.39	$18.40	$18.40
7 purchase totals =	$546.25		$604.7938	$604.78	$604.75	$604.90