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	$58.50	7.140%	$62.6769	$62.68	$62.70	$62.70
Purchase #2	$36.90	8.630%	$40.0845	$40.08	$40.10	$40.10
Purchase #3	$81.31	13.228%	$92.0657	$92.07	$92.05	$92.10
Purchase #4	$162.34	5.198%	$170.7784	$170.78	$170.80	$170.80
Purchase #5	$127.26	11.861%	$142.3543	$142.35	$142.35	$142.40
Purchase #6	$180.32	5.147%	$189.6011	$189.60	$189.60	$189.60
Purchase #7	$242.59	5.659%	$256.3182	$256.32	$256.30	$256.30
7 purchase totals =	$889.22		$953.8791	$953.88	$953.90	$954.00