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	$178.85	12.112%	$200.5123	$200.51	$200.50	$200.50
Purchase #2	$101.29	4.163%	$105.5067	$105.51	$105.50	$105.50
Purchase #3	$63.26	4.620%	$66.1826	$66.18	$66.20	$66.20
Purchase #4	$148.25	11.191%	$164.8407	$164.84	$164.85	$164.80
Purchase #5	$199.90	10.429%	$220.7476	$220.75	$220.75	$220.70
Purchase #6	$171.83	5.771%	$181.7463	$181.75	$181.75	$181.70
Purchase #7	$110.93	5.369%	$116.8858	$116.89	$116.90	$116.90
7 purchase totals =	$974.31		$1,056.4220	$1,056.43	$1,056.45	$1,056.30