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 $197.81   8.555%   $214.7326   $214.73   $214.75   $214.70  
  Purchase #2 $82.34   5.707%   $87.0391   $87.04   $87.05   $87.00  
  Purchase #3 $150.91   6.311%   $160.4339   $160.43   $160.45   $160.40  
  Purchase #4 $17.59   9.528%   $19.266   $19.27   $19.25   $19.30  
  Purchase #5 $220.85   6.407%   $234.9999   $235.00   $235.00   $235.00  
  Purchase #6 $79.95   7.334%   $85.8135   $85.81   $85.80   $85.80  
  Purchase #7 $234.71   11.222%   $261.0492   $261.05   $261.05   $261.00  
  7 purchase totals = $984.16       $1,063.3342   $1,063.33   $1,063.35   $1,063.20