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 $57.59   8.112%   $62.2617   $62.26   $62.25   $62.30  
  Purchase #2 $212.46   3.507%   $219.911   $219.91   $219.90   $219.90  
  Purchase #3 $171.95   11.412%   $191.5729   $191.57   $191.55   $191.60  
  Purchase #4 $87.96   10.852%   $97.5054   $97.51   $97.50   $97.50  
  Purchase #5 $207.60   9.642%   $227.6168   $227.62   $227.60   $227.60  
  Purchase #6 $211.81   10.422%   $233.8848   $233.88   $233.90   $233.90  
  Purchase #7 $21.97   11.522%   $24.5014   $24.50   $24.50   $24.50  
  7 purchase totals = $971.34       $1,057.2540   $1,057.25   $1,057.20   $1,057.30