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 $216.51   7.164%   $232.0208   $232.02   $232.00   $232.00  
  Purchase #2 $55.27   12.174%   $61.9986   $62.00   $62.00   $62.00  
  Purchase #3 $228.33   6.872%   $244.0208   $244.02   $244.00   $244.00  
  Purchase #4 $136.39   5.869%   $144.3947   $144.39   $144.40   $144.40  
  Purchase #5 $245.75   4.659%   $257.1995   $257.20   $257.20   $257.20  
  Purchase #6 $191.93   8.264%   $207.7911   $207.79   $207.80   $207.80  
  Purchase #7 $77.51   13.641%   $88.0831   $88.08   $88.10   $88.10  
  7 purchase totals = $1,151.69       $1,235.5086   $1,235.50   $1,235.50   $1,235.50