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	$133.78	6.329%	$142.2469	$142.25	$142.25	$142.20
Purchase #2	$80.46	7.464%	$86.4655	$86.47	$86.45	$86.50
Purchase #3	$53.86	6.818%	$57.5322	$57.53	$57.55	$57.50
Purchase #4	$29.70	7.184%	$31.8336	$31.83	$31.85	$31.80
Purchase #5	$112.64	7.723%	$121.3392	$121.34	$121.35	$121.30
Purchase #6	$131.62	7.850%	$141.9522	$141.95	$141.95	$142.00
Purchase #7	$87.67	13.356%	$99.3792	$99.38	$99.40	$99.40
7 purchase totals =	$629.73		$680.7488	$680.75	$680.80	$680.70