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	$39.37	10.279%	$43.4168	$43.42	$43.40	$43.40
Purchase #2	$40.66	11.382%	$45.2879	$45.29	$45.30	$45.30
Purchase #3	$229.86	7.329%	$246.7064	$246.71	$246.70	$246.70
Purchase #4	$120.72	4.718%	$126.4156	$126.42	$126.40	$126.40
Purchase #5	$59.73	12.327%	$67.0929	$67.09	$67.10	$67.10
Purchase #6	$204.34	10.341%	$225.4708	$225.47	$225.45	$225.50
Purchase #7	$169.85	7.642%	$182.8299	$182.83	$182.85	$182.80
7 purchase totals =	$864.53		$937.2203	$937.23	$937.20	$937.20