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	$170.53	3.228%	$176.0347	$176.03	$176.05	$176.00
Purchase #2	$34.68	8.441%	$37.6073	$37.61	$37.60	$37.60
Purchase #3	$174.55	8.363%	$189.1476	$189.15	$189.15	$189.10
Purchase #4	$100.85	3.827%	$104.7095	$104.71	$104.70	$104.70
Purchase #5	$135.49	11.491%	$151.0592	$151.06	$151.05	$151.10
Purchase #6	$171.41	11.300%	$190.7793	$190.78	$190.80	$190.80
Purchase #7	$192.29	9.482%	$210.5229	$210.52	$210.50	$210.50
7 purchase totals =	$979.80		$1,059.8605	$1,059.86	$1,059.85	$1,059.80