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	$177.83	11.487%	$198.2573	$198.26	$198.25	$198.30
Purchase #2	$85.39	6.410%	$90.8635	$90.86	$90.85	$90.90
Purchase #3	$36.25	5.267%	$38.1593	$38.16	$38.15	$38.20
Purchase #4	$119.57	5.268%	$125.8689	$125.87	$125.85	$125.90
Purchase #5	$138.32	10.593%	$152.9722	$152.97	$152.95	$153.00
Purchase #6	$149.61	12.832%	$168.808	$168.81	$168.80	$168.80
Purchase #7	$135.48	8.144%	$146.5135	$146.51	$146.50	$146.50
7 purchase totals =	$842.45		$921.4427	$921.44	$921.35	$921.60