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 $91.85   3.359%   $94.9352   $94.94   $94.95   $94.90  
  Purchase #2 $212.37   8.164%   $229.7079   $229.71   $229.70   $229.70  
  Purchase #3 $151.65   7.670%   $163.2816   $163.28   $163.30   $163.30  
  Purchase #4 $136.35   3.620%   $141.2859   $141.29   $141.30   $141.30  
  Purchase #5 $209.86   6.329%   $223.142   $223.14   $223.15   $223.10  
  Purchase #6 $167.26   12.836%   $188.7295   $188.73   $188.75   $188.70  
  Purchase #7 $124.83   5.508%   $131.7056   $131.71   $131.70   $131.70  
  7 purchase totals = $1,094.17       $1,172.7877   $1,172.80   $1,172.85   $1,172.70