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 $112.49   12.745%   $126.8269   $126.83   $126.85   $126.80  
  Purchase #2 $207.90   8.719%   $226.0268   $226.03   $226.05   $226.00  
  Purchase #3 $59.96   10.246%   $66.1035   $66.10   $66.10   $66.10  
  Purchase #4 $215.44   9.564%   $236.0447   $236.04   $236.05   $236.00  
  Purchase #5 $172.28   3.870%   $178.9472   $178.95   $178.95   $178.90  
  Purchase #6 $215.95   7.492%   $232.129   $232.13   $232.15   $232.10  
  Purchase #7 $76.72   11.362%   $85.4369   $85.44   $85.45   $85.40  
  7 purchase totals = $1,060.74       $1,151.5150   $1,151.52   $1,151.60   $1,151.30