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 $85.27   12.153%   $95.6329   $95.63   $95.65   $95.60  
  Purchase #2 $204.80   6.327%   $217.7577   $217.76   $217.75   $217.80  
  Purchase #3 $222.72   3.132%   $229.6956   $229.70   $229.70   $229.70  
  Purchase #4 $211.84   7.122%   $226.9272   $226.93   $226.95   $226.90  
  Purchase #5 $123.98   12.588%   $139.5866   $139.59   $139.60   $139.60  
  Purchase #6 $15.80   3.227%   $16.3099   $16.31   $16.30   $16.30  
  Purchase #7 $14.76   4.617%   $15.4415   $15.44   $15.45   $15.40  
  7 purchase totals = $879.17       $941.3514   $941.36   $941.40   $941.30