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 $168.46   10.810%   $186.6705   $186.67   $186.65   $186.70  
  Purchase #2 $218.78   12.559%   $246.2566   $246.26   $246.25   $246.30  
  Purchase #3 $197.42   7.125%   $211.4862   $211.49   $211.50   $211.50  
  Purchase #4 $47.39   13.159%   $53.6261   $53.63   $53.65   $53.60  
  Purchase #5 $130.81   6.744%   $139.6318   $139.63   $139.65   $139.60  
  Purchase #6 $202.56   5.610%   $213.9236   $213.92   $213.90   $213.90  
  Purchase #7 $58.52   11.341%   $65.1568   $65.16   $65.15   $65.20  
  7 purchase totals = $1,023.94       $1,116.7516   $1,116.76   $1,116.75   $1,116.80