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	$102.44	10.529%	$113.2259	$113.23	$113.25	$113.20
Purchase #2	$35.61	8.575%	$38.6636	$38.66	$38.65	$38.70
Purchase #3	$36.69	7.676%	$39.5063	$39.51	$39.50	$39.50
Purchase #4	$166.75	3.684%	$172.8931	$172.89	$172.90	$172.90
Purchase #5	$150.77	3.392%	$155.8841	$155.88	$155.90	$155.90
Purchase #6	$164.93	5.585%	$174.1413	$174.14	$174.15	$174.10
Purchase #7	$112.79	13.661%	$128.1982	$128.20	$128.20	$128.20
7 purchase totals =	$769.98		$822.5125	$822.51	$822.55	$822.50