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 $96.31   9.561%   $105.5182   $105.52   $105.50   $105.50  
  Purchase #2 $199.25   8.514%   $216.2141   $216.21   $216.20   $216.20  
  Purchase #3 $33.46   5.227%   $35.209   $35.21   $35.20   $35.20  
  Purchase #4 $160.95   6.179%   $170.8951   $170.90   $170.90   $170.90  
  Purchase #5 $69.53   12.168%   $77.9904   $77.99   $78.00   $78.00  
  Purchase #6 $191.56   10.820%   $212.2868   $212.29   $212.30   $212.30  
  Purchase #7 $190.76   9.321%   $208.5407   $208.54   $208.55   $208.50  
  7 purchase totals = $941.82       $1,026.6543   $1,026.66   $1,026.65   $1,026.60