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 $118.25   6.257%   $125.6489   $125.65   $125.65   $125.60  
  Purchase #2 $207.95   12.495%   $233.9334   $233.93   $233.95   $233.90  
  Purchase #3 $238.27   10.576%   $263.4694   $263.47   $263.45   $263.50  
  Purchase #4 $244.84   9.813%   $268.8661   $268.87   $268.85   $268.90  
  Purchase #5 $163.34   6.767%   $174.3932   $174.39   $174.40   $174.40  
  Purchase #6 $222.59   6.479%   $237.0116   $237.01   $237.00   $237.00  
  Purchase #7 $121.72   3.563%   $126.0569   $126.06   $126.05   $126.10  
  7 purchase totals = $1,316.96       $1,429.3795   $1,429.38   $1,429.35   $1,429.40