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	$76.80	11.210%	$85.4093	$85.41	$85.40	$85.40
Purchase #2	$196.43	13.326%	$222.6063	$222.61	$222.60	$222.60
Purchase #3	$244.95	12.335%	$275.1646	$275.16	$275.15	$275.20
Purchase #4	$26.46	7.437%	$28.4278	$28.43	$28.45	$28.40
Purchase #5	$100.99	8.545%	$109.6196	$109.62	$109.60	$109.60
Purchase #6	$83.28	10.838%	$92.3059	$92.31	$92.30	$92.30
Purchase #7	$40.46	7.705%	$43.5774	$43.58	$43.60	$43.60
7 purchase totals =	$769.37		$857.1109	$857.12	$857.10	$857.10