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 $183.68   7.616%   $197.6691   $197.67   $197.65   $197.70  
  Purchase #2 $151.25   10.544%   $167.1978   $167.20   $167.20   $167.20  
  Purchase #3 $23.60   6.508%   $25.1359   $25.14   $25.15   $25.10  
  Purchase #4 $51.92   10.151%   $57.1904   $57.19   $57.20   $57.20  
  Purchase #5 $144.52   12.190%   $162.137   $162.14   $162.15   $162.10  
  Purchase #6 $158.51   7.659%   $170.6503   $170.65   $170.65   $170.70  
  Purchase #7 $234.45   8.740%   $254.9409   $254.94   $254.95   $254.90  
  7 purchase totals = $947.93       $1,034.9214   $1,034.93   $1,034.95   $1,034.90