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	$184.68	7.686%	$198.8745	$198.87	$198.85	$198.90
Purchase #2	$177.92	9.343%	$194.5431	$194.54	$194.55	$194.50
Purchase #3	$40.34	5.401%	$42.5188	$42.52	$42.50	$42.50
Purchase #4	$209.35	8.177%	$226.4685	$226.47	$226.45	$226.50
Purchase #5	$147.73	11.304%	$164.4294	$164.43	$164.45	$164.40
Purchase #6	$122.38	3.134%	$126.2154	$126.22	$126.20	$126.20
Purchase #7	$18.39	11.364%	$20.4798	$20.48	$20.50	$20.50
7 purchase totals =	$900.79		$973.5295	$973.53	$973.50	$973.50