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	$132.85	13.615%	$150.9375	$150.94	$150.95	$150.90
Purchase #2	$38.74	8.763%	$42.1348	$42.13	$42.15	$42.10
Purchase #3	$232.88	10.192%	$256.6151	$256.62	$256.60	$256.60
Purchase #4	$112.40	7.558%	$120.8952	$120.90	$120.90	$120.90
Purchase #5	$238.99	13.863%	$272.1212	$272.12	$272.10	$272.10
Purchase #6	$156.95	9.222%	$171.4239	$171.42	$171.40	$171.40
Purchase #7	$98.97	5.766%	$104.6766	$104.68	$104.70	$104.70
7 purchase totals =	$1,011.78		$1,118.8043	$1,118.81	$1,118.80	$1,118.70