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 $93.65   8.761%   $101.8547   $101.85   $101.85   $101.90  
  Purchase #2 $112.87   4.144%   $117.5473   $117.55   $117.55   $117.50  
  Purchase #3 $20.31   11.701%   $22.6865   $22.69   $22.70   $22.70  
  Purchase #4 $127.28   11.322%   $141.6906   $141.69   $141.70   $141.70  
  Purchase #5 $60.37   3.102%   $62.2427   $62.24   $62.25   $62.20  
  Purchase #6 $153.45   4.437%   $160.2586   $160.26   $160.25   $160.30  
  Purchase #7 $84.83   11.659%   $94.7203   $94.72   $94.70   $94.70  
  7 purchase totals = $652.76       $701.0007   $701.00   $701.00   $701.00