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	$168.68	11.323%	$187.7796	$187.78	$187.80	$187.80
Purchase #2	$80.50	9.530%	$88.1717	$88.17	$88.15	$88.20
Purchase #3	$137.83	3.669%	$142.887	$142.89	$142.90	$142.90
Purchase #4	$139.40	11.494%	$155.4226	$155.42	$155.40	$155.40
Purchase #5	$159.36	3.237%	$164.5185	$164.52	$164.50	$164.50
Purchase #6	$9.88	3.479%	$10.2237	$10.22	$10.20	$10.20
Purchase #7	$170.51	5.250%	$179.4618	$179.46	$179.45	$179.50
7 purchase totals =	$866.16		$928.4649	$928.46	$928.40	$928.50