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	$70.78	9.103%	$77.2231	$77.22	$77.20	$77.20
Purchase #2	$126.96	3.504%	$131.4087	$131.41	$131.40	$131.40
Purchase #3	$45.28	9.529%	$49.5947	$49.59	$49.60	$49.60
Purchase #4	$100.77	11.132%	$111.9877	$111.99	$112.00	$112.00
Purchase #5	$151.57	7.494%	$162.9287	$162.93	$162.95	$162.90
Purchase #6	$100.61	9.269%	$109.9355	$109.94	$109.95	$109.90
Purchase #7	$32.29	4.376%	$33.703	$33.70	$33.70	$33.70
7 purchase totals =	$628.26		$676.7814	$676.78	$676.80	$676.70