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 $177.67   13.111%   $200.9643   $200.96   $200.95   $201.00  
  Purchase #2 $227.36   8.181%   $245.9603   $245.96   $245.95   $246.00  
  Purchase #3 $249.87   8.135%   $270.1969   $270.20   $270.20   $270.20  
  Purchase #4 $166.52   6.252%   $176.9308   $176.93   $176.95   $176.90  
  Purchase #5 $222.51   3.791%   $230.9454   $230.95   $230.95   $230.90  
  Purchase #6 $75.65   12.619%   $85.1963   $85.20   $85.20   $85.20  
  Purchase #7 $212.58   10.425%   $234.7415   $234.74   $234.75   $234.70  
  7 purchase totals = $1,332.16       $1,444.9355   $1,444.94   $1,444.95   $1,444.90