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	$190.90	9.200%	$208.4628	$208.46	$208.45	$208.50
Purchase #2	$82.73	8.650%	$89.8861	$89.89	$89.90	$89.90
Purchase #3	$114.82	9.745%	$126.0092	$126.01	$126.00	$126.00
Purchase #4	$193.89	6.426%	$206.3494	$206.35	$206.35	$206.30
Purchase #5	$165.36	11.179%	$183.8456	$183.85	$183.85	$183.80
Purchase #6	$124.92	9.177%	$136.3839	$136.38	$136.40	$136.40
Purchase #7	$138.40	5.412%	$145.8902	$145.89	$145.90	$145.90
7 purchase totals =	$1,011.02		$1,096.8272	$1,096.83	$1,096.85	$1,096.80