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 $56.59   9.488%   $61.9593   $61.96   $61.95   $62.00  
  Purchase #2 $245.93   7.590%   $264.5961   $264.60   $264.60   $264.60  
  Purchase #3 $69.84   7.273%   $74.9195   $74.92   $74.90   $74.90  
  Purchase #4 $87.63   11.458%   $97.6706   $97.67   $97.65   $97.70  
  Purchase #5 $128.62   6.805%   $137.3726   $137.37   $137.35   $137.40  
  Purchase #6 $191.98   8.202%   $207.7262   $207.73   $207.75   $207.70  
  Purchase #7 $219.39   10.637%   $242.7265   $242.73   $242.75   $242.70  
  7 purchase totals = $999.98       $1,086.9708   $1,086.98   $1,086.95   $1,087.00