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	$96.53	13.688%	$109.743	$109.74	$109.75	$109.70
Purchase #2	$126.91	10.177%	$139.8256	$139.83	$139.85	$139.80
Purchase #3	$109.33	6.527%	$116.466	$116.47	$116.45	$116.50
Purchase #4	$211.53	7.822%	$228.0759	$228.08	$228.10	$228.10
Purchase #5	$44.34	12.630%	$49.9401	$49.94	$49.95	$49.90
Purchase #6	$211.98	12.476%	$238.4266	$238.43	$238.45	$238.40
Purchase #7	$210.87	5.516%	$222.5016	$222.50	$222.50	$222.50
7 purchase totals =	$1,011.49		$1,104.9788	$1,104.99	$1,105.05	$1,104.90