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	$22.87	11.683%	$25.5419	$25.54	$25.55	$25.50
Purchase #2	$185.56	3.850%	$192.7041	$192.70	$192.70	$192.70
Purchase #3	$195.45	5.402%	$206.0082	$206.01	$206.00	$206.00
Purchase #4	$102.42	4.585%	$107.116	$107.12	$107.10	$107.10
Purchase #5	$230.43	11.499%	$256.9271	$256.93	$256.95	$256.90
Purchase #6	$145.59	3.317%	$150.4192	$150.42	$150.40	$150.40
Purchase #7	$115.42	6.762%	$123.2247	$123.22	$123.20	$123.20
7 purchase totals =	$997.74		$1,061.9412	$1,061.94	$1,061.90	$1,061.80