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	$57.97	5.473%	$61.1427	$61.14	$61.15	$61.10
Purchase #2	$145.92	6.178%	$154.9349	$154.93	$154.95	$154.90
Purchase #3	$75.54	13.827%	$85.9849	$85.98	$86.00	$86.00
Purchase #4	$151.53	4.181%	$157.8655	$157.87	$157.85	$157.90
Purchase #5	$121.85	8.126%	$131.7515	$131.75	$131.75	$131.80
Purchase #6	$29.27	6.144%	$31.0683	$31.07	$31.05	$31.10
Purchase #7	$139.41	8.218%	$150.8667	$150.87	$150.85	$150.90
7 purchase totals =	$721.49		$773.6145	$773.61	$773.60	$773.70