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 $68.77   10.663%   $76.1029   $76.10   $76.10   $76.10  
  Purchase #2 $160.36   3.702%   $166.2965   $166.30   $166.30   $166.30  
  Purchase #3 $144.90   12.352%   $162.798   $162.80   $162.80   $162.80  
  Purchase #4 $68.98   7.471%   $74.1335   $74.13   $74.15   $74.10  
  Purchase #5 $196.91   10.525%   $217.6348   $217.63   $217.65   $217.60  
  Purchase #6 $120.96   12.348%   $135.8961   $135.90   $135.90   $135.90  
  Purchase #7 $179.49   6.254%   $190.7153   $190.72   $190.70   $190.70  
  7 purchase totals = $940.37       $1,023.5771   $1,023.58   $1,023.60   $1,023.50