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	$167.59	11.805%	$187.374	$187.37	$187.35	$187.40
Purchase #2	$133.89	4.260%	$139.5937	$139.59	$139.60	$139.60
Purchase #3	$38.70	4.587%	$40.4752	$40.48	$40.50	$40.50
Purchase #4	$201.81	4.340%	$210.5686	$210.57	$210.55	$210.60
Purchase #5	$114.94	8.423%	$124.6214	$124.62	$124.60	$124.60
Purchase #6	$150.95	7.709%	$162.5867	$162.59	$162.60	$162.60
Purchase #7	$167.32	10.857%	$185.4859	$185.49	$185.50	$185.50
7 purchase totals =	$975.20		$1,050.7055	$1,050.71	$1,050.70	$1,050.80