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 $59.84   3.592%   $61.9895   $61.99   $62.00   $62.00  
  Purchase #2 $250.96   4.770%   $262.9308   $262.93   $262.95   $262.90  
  Purchase #3 $169.98   12.391%   $191.0422   $191.04   $191.05   $191.00  
  Purchase #4 $106.25   3.548%   $110.0198   $110.02   $110.00   $110.00  
  Purchase #5 $202.56   3.336%   $209.3174   $209.32   $209.30   $209.30  
  Purchase #6 $77.56   10.130%   $85.4168   $85.42   $85.40   $85.40  
  Purchase #7 $79.38   6.167%   $84.2754   $84.28   $84.30   $84.30  
  7 purchase totals = $946.53       $1,004.9919   $1,005.00   $1,005.00   $1,004.90