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	$106.32	12.677%	$119.7982	$119.80	$119.80	$119.80
Purchase #2	$78.51	5.608%	$82.9128	$82.91	$82.90	$82.90
Purchase #3	$137.79	6.152%	$146.2668	$146.27	$146.25	$146.30
Purchase #4	$199.25	9.202%	$217.585	$217.59	$217.60	$217.60
Purchase #5	$9.60	7.753%	$10.3443	$10.34	$10.35	$10.30
Purchase #6	$171.59	12.406%	$192.8775	$192.88	$192.90	$192.90
Purchase #7	$232.98	13.676%	$264.8423	$264.84	$264.85	$264.80
7 purchase totals =	$936.04		$1,034.6269	$1,034.63	$1,034.65	$1,034.60