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	$222.30	4.233%	$231.71	$231.71	$231.70	$231.70
Purchase #2	$180.92	9.162%	$197.4959	$197.50	$197.50	$197.50
Purchase #3	$164.40	11.406%	$183.1515	$183.15	$183.15	$183.20
Purchase #4	$75.39	4.275%	$78.6129	$78.61	$78.60	$78.60
Purchase #5	$238.89	3.500%	$247.2512	$247.25	$247.25	$247.30
Purchase #6	$36.78	4.632%	$38.4836	$38.48	$38.50	$38.50
Purchase #7	$187.66	13.254%	$212.5325	$212.53	$212.55	$212.50
7 purchase totals =	$1,106.34		$1,189.2376	$1,189.23	$1,189.25	$1,189.30