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 $161.65   8.777%   $175.838   $175.84   $175.85   $175.80  
  Purchase #2 $12.79   8.208%   $13.8398   $13.84   $13.85   $13.80  
  Purchase #3 $63.76   3.435%   $65.9502   $65.95   $65.95   $66.00  
  Purchase #4 $230.45   8.566%   $250.1903   $250.19   $250.20   $250.20  
  Purchase #5 $216.69   12.556%   $243.8976   $243.90   $243.90   $243.90  
  Purchase #6 $227.31   9.595%   $249.1204   $249.12   $249.10   $249.10  
  Purchase #7 $164.98   7.822%   $177.8847   $177.88   $177.90   $177.90  
  7 purchase totals = $1,077.63       $1,176.7210   $1,176.72   $1,176.75   $1,176.70