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	$31.29	12.544%	$35.215	$35.22	$35.20	$35.20
Purchase #2	$126.47	4.254%	$131.85	$131.85	$131.85	$131.90
Purchase #3	$133.45	8.850%	$145.2603	$145.26	$145.25	$145.30
Purchase #4	$87.64	13.526%	$99.4942	$99.49	$99.50	$99.50
Purchase #5	$61.31	5.844%	$64.893	$64.89	$64.90	$64.90
Purchase #6	$87.99	3.369%	$90.9544	$90.95	$90.95	$91.00
Purchase #7	$100.58	6.108%	$106.7234	$106.72	$106.70	$106.70
7 purchase totals =	$628.73		$674.3903	$674.38	$674.35	$674.50