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	$151.94	3.258%	$156.8902	$156.89	$156.90	$156.90
Purchase #2	$155.54	7.826%	$167.7126	$167.71	$167.70	$167.70
Purchase #3	$117.34	5.142%	$123.3736	$123.37	$123.35	$123.40
Purchase #4	$101.56	9.518%	$111.2265	$111.23	$111.25	$111.20
Purchase #5	$245.73	10.771%	$272.1976	$272.20	$272.20	$272.20
Purchase #6	$145.25	5.480%	$153.2097	$153.21	$153.20	$153.20
Purchase #7	$158.89	11.257%	$176.7762	$176.78	$176.80	$176.80
7 purchase totals =	$1,076.25		$1,161.3864	$1,161.39	$1,161.40	$1,161.40