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	$92.82	7.464%	$99.7481	$99.75	$99.75	$99.70
Purchase #2	$95.97	7.841%	$103.495	$103.50	$103.50	$103.50
Purchase #3	$87.86	6.659%	$93.7106	$93.71	$93.70	$93.70
Purchase #4	$164.55	8.251%	$178.127	$178.13	$178.15	$178.10
Purchase #5	$110.85	13.676%	$126.0098	$126.01	$126.00	$126.00
Purchase #6	$51.98	5.636%	$54.9096	$54.91	$54.90	$54.90
Purchase #7	$131.47	7.722%	$141.6221	$141.62	$141.60	$141.60
7 purchase totals =	$735.50		$797.6222	$797.63	$797.60	$797.50