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 $119.26   11.476%   $132.9463   $132.95   $132.95   $132.90  
  Purchase #2 $32.93   10.260%   $36.3086   $36.31   $36.30   $36.30  
  Purchase #3 $148.82   12.656%   $167.6547   $167.65   $167.65   $167.70  
  Purchase #4 $225.93   6.346%   $240.2675   $240.27   $240.25   $240.30  
  Purchase #5 $192.96   12.757%   $217.5759   $217.58   $217.60   $217.60  
  Purchase #6 $12.46   3.792%   $12.9325   $12.93   $12.95   $12.90  
  Purchase #7 $156.32   13.859%   $177.9844   $177.98   $178.00   $178.00  
  7 purchase totals = $888.68       $985.6699   $985.67   $985.70   $985.70