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	$202.43	7.105%	$216.8127	$216.81	$216.80	$216.80
Purchase #2	$62.32	4.664%	$65.2266	$65.23	$65.25	$65.20
Purchase #3	$126.51	13.585%	$143.6964	$143.70	$143.70	$143.70
Purchase #4	$146.29	12.433%	$164.4782	$164.48	$164.50	$164.50
Purchase #5	$58.71	10.511%	$64.881	$64.88	$64.90	$64.90
Purchase #6	$11.50	8.170%	$12.4396	$12.44	$12.45	$12.40
Purchase #7	$86.38	5.374%	$91.0221	$91.02	$91.00	$91.00
7 purchase totals =	$694.14		$758.5566	$758.56	$758.60	$758.50