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 $66.85   11.452%   $74.5057   $74.51   $74.50   $74.50  
  Purchase #2 $91.37   5.512%   $96.4063   $96.41   $96.40   $96.40  
  Purchase #3 $109.49   8.370%   $118.6543   $118.65   $118.65   $118.70  
  Purchase #4 $232.82   12.312%   $261.4848   $261.48   $261.50   $261.50  
  Purchase #5 $93.62   8.868%   $101.9222   $101.92   $101.90   $101.90  
  Purchase #6 $240.46   5.186%   $252.9303   $252.93   $252.95   $252.90  
  Purchase #7 $138.58   4.295%   $144.532   $144.53   $144.55   $144.50  
  7 purchase totals = $973.19       $1,050.4356   $1,050.43   $1,050.45   $1,050.40