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	$126.46	5.464%	$133.3698	$133.37	$133.35	$133.40
Purchase #2	$229.73	3.698%	$238.2254	$238.23	$238.25	$238.20
Purchase #3	$81.72	10.858%	$90.5932	$90.59	$90.60	$90.60
Purchase #4	$246.40	9.781%	$270.5004	$270.50	$270.50	$270.50
Purchase #5	$190.41	12.588%	$214.3788	$214.38	$214.40	$214.40
Purchase #6	$150.46	12.246%	$168.8853	$168.89	$168.90	$168.90
Purchase #7	$123.48	12.528%	$138.9496	$138.95	$138.95	$138.90
7 purchase totals =	$1,148.66		$1,254.9025	$1,254.91	$1,254.95	$1,254.90