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	$75.54	13.781%	$85.9502	$85.95	$85.95	$86.00
Purchase #2	$188.30	4.392%	$196.5701	$196.57	$196.55	$196.60
Purchase #3	$69.45	10.248%	$76.5672	$76.57	$76.55	$76.60
Purchase #4	$229.25	5.221%	$241.2191	$241.22	$241.20	$241.20
Purchase #5	$121.89	12.315%	$136.9008	$136.90	$136.90	$136.90
Purchase #6	$119.44	10.228%	$131.6563	$131.66	$131.65	$131.70
Purchase #7	$250.57	8.322%	$271.4224	$271.42	$271.40	$271.40
7 purchase totals =	$1,054.44		$1,140.2861	$1,140.29	$1,140.20	$1,140.40