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	$125.96	11.543%	$140.4996	$140.50	$140.50	$140.50
Purchase #2	$221.38	11.788%	$247.4763	$247.48	$247.50	$247.50
Purchase #3	$192.65	8.198%	$208.4434	$208.44	$208.45	$208.40
Purchase #4	$165.43	8.564%	$179.5974	$179.60	$179.60	$179.60
Purchase #5	$93.41	7.446%	$100.3653	$100.37	$100.35	$100.40
Purchase #6	$140.49	4.763%	$147.1815	$147.18	$147.20	$147.20
Purchase #7	$104.83	4.821%	$109.8839	$109.88	$109.90	$109.90
7 purchase totals =	$1,044.15		$1,133.4474	$1,133.45	$1,133.50	$1,133.50