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 $94.91   8.469%   $102.9479   $102.95   $102.95   $102.90  
  Purchase #2 $60.61   10.796%   $67.1535   $67.15   $67.15   $67.20  
  Purchase #3 $6.63   12.632%   $7.4675   $7.47   $7.45   $7.50  
  Purchase #4 $86.27   5.252%   $90.8009   $90.80   $90.80   $90.80  
  Purchase #5 $29.74   12.764%   $33.536   $33.54   $33.55   $33.50  
  Purchase #6 $203.50   11.159%   $226.2086   $226.21   $226.20   $226.20  
  Purchase #7 $231.67   5.310%   $243.9717   $243.97   $243.95   $244.00  
  7 purchase totals = $713.33       $772.0861   $772.09   $772.05   $772.10