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 $234.65   11.814%   $262.3716   $262.37   $262.35   $262.40  
  Purchase #2 $245.72   8.690%   $267.0731   $267.07   $267.05   $267.10  
  Purchase #3 $121.65   10.188%   $134.0437   $134.04   $134.05   $134.00  
  Purchase #4 $154.42   5.121%   $162.3278   $162.33   $162.35   $162.30  
  Purchase #5 $115.60   6.389%   $122.9857   $122.99   $123.00   $123.00  
  Purchase #6 $81.86   6.541%   $87.2145   $87.21   $87.20   $87.20  
  Purchase #7 $62.65   7.391%   $67.2805   $67.28   $67.30   $67.30  
  7 purchase totals = $1,016.55       $1,103.2969   $1,103.29   $1,103.30   $1,103.30