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 $87.58   9.236%   $95.6689   $95.67   $95.65   $95.70  
  Purchase #2 $238.50   6.659%   $254.3817   $254.38   $254.40   $254.40  
  Purchase #3 $215.35   12.560%   $242.398   $242.40   $242.40   $242.40  
  Purchase #4 $236.77   11.458%   $263.8991   $263.90   $263.90   $263.90  
  Purchase #5 $94.81   5.780%   $100.29   $100.29   $100.30   $100.30  
  Purchase #6 $224.67   3.682%   $232.9423   $232.94   $232.95   $232.90  
  Purchase #7 $126.87   6.711%   $135.3842   $135.38   $135.40   $135.40  
  7 purchase totals = $1,224.55       $1,324.9642   $1,324.96   $1,325.00   $1,325.00