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	$140.49	11.660%	$156.8711	$156.87	$156.85	$156.90
Purchase #2	$125.27	4.732%	$131.1978	$131.20	$131.20	$131.20
Purchase #3	$132.90	11.626%	$148.351	$148.35	$148.35	$148.40
Purchase #4	$136.74	3.538%	$141.5779	$141.58	$141.60	$141.60
Purchase #5	$69.78	3.175%	$71.9955	$72.00	$72.00	$72.00
Purchase #6	$218.28	10.225%	$240.5991	$240.60	$240.60	$240.60
Purchase #7	$111.32	6.655%	$118.7283	$118.73	$118.75	$118.70
7 purchase totals =	$934.78		$1,009.3207	$1,009.33	$1,009.35	$1,009.40