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 $67.33   13.393%   $76.3475   $76.35   $76.35   $76.30  
  Purchase #2 $214.32   9.112%   $233.8488   $233.85   $233.85   $233.80  
  Purchase #3 $18.65   13.803%   $21.2243   $21.22   $21.20   $21.20  
  Purchase #4 $59.96   6.208%   $63.6823   $63.68   $63.70   $63.70  
  Purchase #5 $228.40   11.776%   $255.2964   $255.30   $255.30   $255.30  
  Purchase #6 $187.60   9.464%   $205.3545   $205.35   $205.35   $205.40  
  Purchase #7 $224.37   13.744%   $255.2074   $255.21   $255.20   $255.20  
  7 purchase totals = $1,000.63       $1,110.9612   $1,110.96   $1,110.95   $1,110.90