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 $86.90   10.755%   $96.2461   $96.25   $96.25   $96.20  
  Purchase #2 $227.26   5.257%   $239.2071   $239.21   $239.20   $239.20  
  Purchase #3 $199.31   11.462%   $222.1549   $222.15   $222.15   $222.20  
  Purchase #4 $43.98   13.516%   $49.9243   $49.92   $49.90   $49.90  
  Purchase #5 $56.96   6.217%   $60.5012   $60.50   $60.50   $60.50  
  Purchase #6 $58.57   6.352%   $62.2904   $62.29   $62.30   $62.30  
  Purchase #7 $157.80   9.470%   $172.7437   $172.74   $172.75   $172.70  
  7 purchase totals = $830.78       $903.0677   $903.06   $903.05   $903.00