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 $46.36   4.811%   $48.5904   $48.59   $48.60   $48.60  
  Purchase #2 $98.26   8.497%   $106.6092   $106.61   $106.60   $106.60  
  Purchase #3 $206.69   7.334%   $221.8486   $221.85   $221.85   $221.80  
  Purchase #4 $19.48   8.771%   $21.1886   $21.19   $21.20   $21.20  
  Purchase #5 $125.97   8.499%   $136.6762   $136.68   $136.70   $136.70  
  Purchase #6 $201.60   12.425%   $226.6488   $226.65   $226.65   $226.60  
  Purchase #7 $5.26   9.303%   $5.7493   $5.75   $5.75   $5.70  
  7 purchase totals = $703.62       $767.3111   $767.32   $767.35   $767.20