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 $196.60   4.751%   $205.9405   $205.94   $205.95   $205.90  
  Purchase #2 $160.46   10.617%   $177.496   $177.50   $177.50   $177.50  
  Purchase #3 $123.49   9.529%   $135.2574   $135.26   $135.25   $135.30  
  Purchase #4 $61.92   9.765%   $67.9665   $67.97   $67.95   $68.00  
  Purchase #5 $242.29   13.820%   $275.7745   $275.77   $275.75   $275.80  
  Purchase #6 $162.85   7.542%   $175.1321   $175.13   $175.15   $175.10  
  Purchase #7 $102.82   6.313%   $109.311   $109.31   $109.30   $109.30  
  7 purchase totals = $1,050.43       $1,146.8780   $1,146.88   $1,146.85   $1,146.90