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	$140.46	11.224%	$156.2252	$156.23	$156.25	$156.20
Purchase #2	$156.92	5.109%	$164.937	$164.94	$164.95	$164.90
Purchase #3	$87.67	4.285%	$91.4267	$91.43	$91.45	$91.40
Purchase #4	$10.30	6.263%	$10.9451	$10.95	$10.95	$10.90
Purchase #5	$221.37	13.123%	$250.4204	$250.42	$250.40	$250.40
Purchase #6	$127.51	13.193%	$144.3324	$144.33	$144.35	$144.30
Purchase #7	$169.68	9.848%	$186.3901	$186.39	$186.40	$186.40
7 purchase totals =	$913.91		$1,004.6769	$1,004.69	$1,004.75	$1,004.50