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	$101.70	11.714%	$113.6131	$113.61	$113.60	$113.60
Purchase #2	$193.81	8.227%	$209.7547	$209.75	$209.75	$209.80
Purchase #3	$100.84	8.273%	$109.1825	$109.18	$109.20	$109.20
Purchase #4	$115.77	4.298%	$120.7458	$120.75	$120.75	$120.70
Purchase #5	$179.66	11.828%	$200.9102	$200.91	$200.90	$200.90
Purchase #6	$237.42	12.397%	$266.853	$266.85	$266.85	$266.90
Purchase #7	$132.33	3.731%	$137.2672	$137.27	$137.25	$137.30
7 purchase totals =	$1,061.53		$1,158.3265	$1,158.32	$1,158.30	$1,158.40