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 $41.60   5.866%   $44.0403   $44.04   $44.05   $44.00  
  Purchase #2 $136.65   9.552%   $149.7028   $149.70   $149.70   $149.70  
  Purchase #3 $216.84   6.528%   $230.9953   $231.00   $231.00   $231.00  
  Purchase #4 $200.30   5.838%   $211.9935   $211.99   $212.00   $212.00  
  Purchase #5 $159.65   9.235%   $174.3937   $174.39   $174.40   $174.40  
  Purchase #6 $9.59   6.499%   $10.2133   $10.21   $10.20   $10.20  
  Purchase #7 $209.44   11.774%   $234.0995   $234.10   $234.10   $234.10  
  7 purchase totals = $974.07       $1,055.4384   $1,055.43   $1,055.45   $1,055.40