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	$230.69	8.563%	$250.444	$250.44	$250.45	$250.40
Purchase #2	$119.69	9.702%	$131.3023	$131.30	$131.30	$131.30
Purchase #3	$81.46	6.219%	$86.526	$86.53	$86.55	$86.50
Purchase #4	$71.34	13.491%	$80.9645	$80.96	$80.95	$81.00
Purchase #5	$176.25	5.288%	$185.5701	$185.57	$185.55	$185.60
Purchase #6	$200.82	3.331%	$207.5093	$207.51	$207.50	$207.50
Purchase #7	$104.34	9.151%	$113.8882	$113.89	$113.90	$113.90
7 purchase totals =	$984.59		$1,056.2044	$1,056.20	$1,056.20	$1,056.20