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 $94.90   7.487%   $102.0052   $102.01   $102.00   $102.00  
  Purchase #2 $153.54   5.666%   $162.2396   $162.24   $162.25   $162.20  
  Purchase #3 $49.85   8.468%   $54.0713   $54.07   $54.05   $54.10  
  Purchase #4 $244.35   7.332%   $262.2657   $262.27   $262.25   $262.30  
  Purchase #5 $201.41   13.799%   $229.2026   $229.20   $229.20   $229.20  
  Purchase #6 $223.59   7.874%   $241.1955   $241.20   $241.20   $241.20  
  Purchase #7 $209.37   7.812%   $225.726   $225.73   $225.75   $225.70  
  7 purchase totals = $1,177.01       $1,276.7059   $1,276.72   $1,276.70   $1,276.70