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 $176.38   12.628%   $198.6533   $198.65   $198.65   $198.70  
  Purchase #2 $132.62   10.215%   $146.1671   $146.17   $146.15   $146.20  
  Purchase #3 $217.76   6.741%   $232.4392   $232.44   $232.45   $232.40  
  Purchase #4 $74.95   7.206%   $80.3509   $80.35   $80.35   $80.40  
  Purchase #5 $50.68   9.700%   $55.596   $55.60   $55.60   $55.60  
  Purchase #6 $118.80   5.765%   $125.6488   $125.65   $125.65   $125.60  
  Purchase #7 $184.87   13.309%   $209.4743   $209.47   $209.45   $209.50  
  7 purchase totals = $956.06       $1,048.3296   $1,048.33   $1,048.30   $1,048.40