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 $58.61   6.540%   $62.4431   $62.44   $62.45   $62.40  
  Purchase #2 $181.66   7.303%   $194.9266   $194.93   $194.95   $194.90  
  Purchase #3 $148.43   4.222%   $154.6967   $154.70   $154.70   $154.70  
  Purchase #4 $19.54   8.526%   $21.206   $21.21   $21.20   $21.20  
  Purchase #5 $187.94   6.157%   $199.5115   $199.51   $199.50   $199.50  
  Purchase #6 $152.39   12.257%   $171.0684   $171.07   $171.05   $171.10  
  Purchase #7 $213.62   12.670%   $240.6857   $240.69   $240.70   $240.70  
  7 purchase totals = $962.19       $1,044.5380   $1,044.55   $1,044.55   $1,044.50