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 $104.46   8.729%   $113.5783   $113.58   $113.60   $113.60  
  Purchase #2 $186.77   12.450%   $210.0229   $210.02   $210.00   $210.00  
  Purchase #3 $84.36   12.564%   $94.959   $94.96   $94.95   $95.00  
  Purchase #4 $162.84   6.574%   $173.5451   $173.55   $173.55   $173.50  
  Purchase #5 $190.45   12.718%   $214.6714   $214.67   $214.65   $214.70  
  Purchase #6 $95.46   4.107%   $99.3805   $99.38   $99.40   $99.40  
  Purchase #7 $193.70   12.158%   $217.25   $217.25   $217.25   $217.30  
  7 purchase totals = $1,018.04       $1,123.4072   $1,123.41   $1,123.40   $1,123.50