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 $201.42   5.848%   $213.199   $213.20   $213.20   $213.20  
  Purchase #2 $88.29   8.627%   $95.9068   $95.91   $95.90   $95.90  
  Purchase #3 $201.63   4.242%   $210.1831   $210.18   $210.20   $210.20  
  Purchase #4 $197.66   3.430%   $204.4397   $204.44   $204.45   $204.40  
  Purchase #5 $129.27   10.559%   $142.9196   $142.92   $142.90   $142.90  
  Purchase #6 $127.90   8.375%   $138.6116   $138.61   $138.60   $138.60  
  Purchase #7 $120.37   7.717%   $129.659   $129.66   $129.65   $129.70  
  7 purchase totals = $1,066.54       $1,134.9188   $1,134.92   $1,134.90   $1,134.90