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 $60.53   11.635%   $67.5727   $67.57   $67.55   $67.60  
  Purchase #2 $212.41   11.441%   $236.7118   $236.71   $236.70   $236.70  
  Purchase #3 $119.60   3.656%   $123.9726   $123.97   $123.95   $124.00  
  Purchase #4 $23.45   5.620%   $24.7679   $24.77   $24.75   $24.80  
  Purchase #5 $149.41   13.701%   $169.8807   $169.88   $169.90   $169.90  
  Purchase #6 $242.80   9.521%   $265.917   $265.92   $265.90   $265.90  
  Purchase #7 $149.73   8.279%   $162.1261   $162.13   $162.15   $162.10  
  7 purchase totals = $957.93       $1,050.9488   $1,050.95   $1,050.90   $1,051.00