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	$41.62	3.342%	$43.0109	$43.01	$43.00	$43.00
Purchase #2	$145.77	12.185%	$163.5321	$163.53	$163.55	$163.50
Purchase #3	$118.46	10.705%	$131.1411	$131.14	$131.15	$131.10
Purchase #4	$131.72	11.116%	$146.362	$146.36	$146.35	$146.40
Purchase #5	$62.29	6.816%	$66.5357	$66.54	$66.55	$66.50
Purchase #6	$7.48	5.183%	$7.8677	$7.87	$7.85	$7.90
Purchase #7	$178.89	6.421%	$190.3765	$190.38	$190.40	$190.40
7 purchase totals =	$686.23		$748.8260	$748.83	$748.85	$748.80