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	$224.29	9.853%	$246.3893	$246.39	$246.40	$246.40
Purchase #2	$54.81	7.763%	$59.0649	$59.06	$59.05	$59.10
Purchase #3	$133.42	13.163%	$150.9821	$150.98	$151.00	$151.00
Purchase #4	$47.72	12.794%	$53.8253	$53.83	$53.85	$53.80
Purchase #5	$112.72	9.448%	$123.3698	$123.37	$123.35	$123.40
Purchase #6	$46.94	3.274%	$48.4768	$48.48	$48.50	$48.50
Purchase #7	$64.33	11.151%	$71.5034	$71.50	$71.50	$71.50
7 purchase totals =	$684.23		$753.6116	$753.61	$753.65	$753.70