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	$250.49	4.377%	$261.4539	$261.45	$261.45	$261.50
Purchase #2	$223.65	11.162%	$248.6138	$248.61	$248.60	$248.60
Purchase #3	$112.38	11.557%	$125.3678	$125.37	$125.35	$125.40
Purchase #4	$30.76	12.550%	$34.6204	$34.62	$34.60	$34.60
Purchase #5	$104.48	7.541%	$112.3588	$112.36	$112.35	$112.40
Purchase #6	$40.43	12.583%	$45.5173	$45.52	$45.50	$45.50
Purchase #7	$234.89	7.795%	$253.1997	$253.20	$253.20	$253.20
7 purchase totals =	$997.08		$1,081.1317	$1,081.13	$1,081.05	$1,081.20