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	$57.75	4.346%	$60.2598	$60.26	$60.25	$60.30
Purchase #2	$28.99	9.762%	$31.82	$31.82	$31.80	$31.80
Purchase #3	$89.34	5.776%	$94.5003	$94.50	$94.50	$94.50
Purchase #4	$162.83	9.845%	$178.8606	$178.86	$178.85	$178.90
Purchase #5	$125.65	8.564%	$136.4107	$136.41	$136.40	$136.40
Purchase #6	$89.60	12.133%	$100.4712	$100.47	$100.45	$100.50
Purchase #7	$13.48	5.547%	$14.2277	$14.23	$14.25	$14.20
7 purchase totals =	$567.64		$616.5503	$616.55	$616.50	$616.60