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 $181.96   7.611%   $195.809   $195.81   $195.80   $195.80  
  Purchase #2 $52.87   8.477%   $57.3518   $57.35   $57.35   $57.40  
  Purchase #3 $27.28   7.272%   $29.2638   $29.26   $29.25   $29.30  
  Purchase #4 $102.37   5.576%   $108.0782   $108.08   $108.10   $108.10  
  Purchase #5 $106.40   12.141%   $119.318   $119.32   $119.30   $119.30  
  Purchase #6 $78.89   10.514%   $87.1845   $87.18   $87.20   $87.20  
  Purchase #7 $174.71   7.206%   $187.2996   $187.30   $187.30   $187.30  
  7 purchase totals = $724.48       $784.3049   $784.30   $784.30   $784.40