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	$40.97	10.575%	$45.3026	$45.30	$45.30	$45.30
Purchase #2	$238.75	9.601%	$261.6724	$261.67	$261.65	$261.70
Purchase #3	$48.71	11.405%	$54.2654	$54.27	$54.25	$54.30
Purchase #4	$153.30	9.706%	$168.1793	$168.18	$168.20	$168.20
Purchase #5	$48.50	3.588%	$50.2402	$50.24	$50.25	$50.20
Purchase #6	$76.51	6.289%	$81.3217	$81.32	$81.30	$81.30
Purchase #7	$37.48	8.718%	$40.7475	$40.75	$40.75	$40.70
7 purchase totals =	$644.22		$701.7291	$701.73	$701.70	$701.70