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	$197.92	12.423%	$222.5076	$222.51	$222.50	$222.50
Purchase #2	$87.72	12.822%	$98.9675	$98.97	$98.95	$99.00
Purchase #3	$190.65	9.545%	$208.8475	$208.85	$208.85	$208.80
Purchase #4	$78.47	7.767%	$84.5648	$84.56	$84.55	$84.60
Purchase #5	$117.47	8.830%	$127.8426	$127.84	$127.85	$127.80
Purchase #6	$45.69	11.402%	$50.8996	$50.90	$50.90	$50.90
Purchase #7	$245.69	10.663%	$271.8879	$271.89	$271.90	$271.90
7 purchase totals =	$963.61		$1,065.5175	$1,065.52	$1,065.50	$1,065.50