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 $88.82   7.690%   $95.6503   $95.65   $95.65   $95.70  
  Purchase #2 $177.52   3.126%   $183.0693   $183.07   $183.05   $183.10  
  Purchase #3 $80.51   13.642%   $91.4932   $91.49   $91.50   $91.50  
  Purchase #4 $24.88   12.281%   $27.9355   $27.94   $27.95   $27.90  
  Purchase #5 $232.77   12.419%   $261.6777   $261.68   $261.70   $261.70  
  Purchase #6 $216.43   12.286%   $243.0206   $243.02   $243.00   $243.00  
  Purchase #7 $236.71   7.258%   $253.8904   $253.89   $253.90   $253.90  
  7 purchase totals = $1,057.64       $1,156.7370   $1,156.74   $1,156.75   $1,156.80