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 $131.76   8.336%   $142.7435   $142.74   $142.75   $142.70  
  Purchase #2 $235.85   8.357%   $255.56   $255.56   $255.55   $255.60  
  Purchase #3 $75.70   9.592%   $82.9611   $82.96   $82.95   $83.00  
  Purchase #4 $177.60   7.494%   $190.9093   $190.91   $190.90   $190.90  
  Purchase #5 $97.66   5.436%   $102.9688   $102.97   $102.95   $103.00  
  Purchase #6 $195.52   8.681%   $212.4931   $212.49   $212.50   $212.50  
  Purchase #7 $58.69   6.252%   $62.3593   $62.36   $62.35   $62.40  
  7 purchase totals = $972.78       $1,049.9951   $1,049.99   $1,049.95   $1,050.10