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	$82.61	12.466%	$92.9082	$92.91	$92.90	$92.90
Purchase #2	$213.31	10.840%	$236.4328	$236.43	$236.45	$236.40
Purchase #3	$106.89	11.817%	$119.5212	$119.52	$119.50	$119.50
Purchase #4	$202.76	3.633%	$210.1263	$210.13	$210.15	$210.10
Purchase #5	$189.34	8.548%	$205.5248	$205.52	$205.50	$205.50
Purchase #6	$126.77	9.858%	$139.267	$139.27	$139.25	$139.30
Purchase #7	$16.78	12.688%	$18.909	$18.91	$18.90	$18.90
7 purchase totals =	$938.46		$1,022.6893	$1,022.69	$1,022.65	$1,022.60