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	$214.48	5.474%	$226.2206	$226.22	$226.20	$226.20
Purchase #2	$179.38	11.175%	$199.4257	$199.43	$199.45	$199.40
Purchase #3	$242.51	3.289%	$250.4862	$250.49	$250.50	$250.50
Purchase #4	$119.63	6.694%	$127.638	$127.64	$127.65	$127.60
Purchase #5	$83.96	10.127%	$92.4626	$92.46	$92.45	$92.50
Purchase #6	$169.32	12.780%	$190.9591	$190.96	$190.95	$191.00
Purchase #7	$168.52	12.291%	$189.2328	$189.23	$189.25	$189.20
7 purchase totals =	$1,177.80		$1,276.4250	$1,276.43	$1,276.45	$1,276.40