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	$51.67	11.431%	$57.5764	$57.58	$57.60	$57.60
Purchase #2	$168.72	3.195%	$174.1106	$174.11	$174.10	$174.10
Purchase #3	$31.69	11.653%	$35.3828	$35.38	$35.40	$35.40
Purchase #4	$13.78	11.165%	$15.3185	$15.32	$15.30	$15.30
Purchase #5	$162.28	6.736%	$173.2112	$173.21	$173.20	$173.20
Purchase #6	$77.59	11.650%	$86.6292	$86.63	$86.65	$86.60
Purchase #7	$77.49	10.796%	$85.8558	$85.86	$85.85	$85.90
7 purchase totals =	$583.22		$628.0845	$628.09	$628.10	$628.10