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	$126.28	4.485%	$131.9437	$131.94	$131.95	$131.90
Purchase #2	$39.42	7.247%	$42.2768	$42.28	$42.30	$42.30
Purchase #3	$197.94	11.685%	$221.0693	$221.07	$221.05	$221.10
Purchase #4	$98.43	3.455%	$101.8308	$101.83	$101.85	$101.80
Purchase #5	$182.86	5.375%	$192.6887	$192.69	$192.70	$192.70
Purchase #6	$207.72	13.662%	$236.0987	$236.10	$236.10	$236.10
Purchase #7	$168.90	8.632%	$183.4794	$183.48	$183.50	$183.50
7 purchase totals =	$1,021.55		$1,109.3874	$1,109.39	$1,109.45	$1,109.40