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	$113.71	9.802%	$124.8559	$124.86	$124.85	$124.90
Purchase #2	$202.40	4.840%	$212.1962	$212.20	$212.20	$212.20
Purchase #3	$177.87	10.537%	$196.6122	$196.61	$196.60	$196.60
Purchase #4	$68.68	4.161%	$71.5378	$71.54	$71.55	$71.50
Purchase #5	$82.38	6.589%	$87.808	$87.81	$87.80	$87.80
Purchase #6	$151.81	3.337%	$156.8759	$156.88	$156.90	$156.90
Purchase #7	$28.66	12.760%	$32.317	$32.32	$32.30	$32.30
7 purchase totals =	$825.51		$882.2030	$882.22	$882.20	$882.20