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 $241.65   11.426%   $269.2609   $269.26   $269.25   $269.30  
  Purchase #2 $31.85   8.653%   $34.606   $34.61   $34.60   $34.60  
  Purchase #3 $40.85   8.682%   $44.3966   $44.40   $44.40   $44.40  
  Purchase #4 $130.46   11.586%   $145.5751   $145.58   $145.60   $145.60  
  Purchase #5 $187.60   11.647%   $209.4498   $209.45   $209.45   $209.40  
  Purchase #6 $181.60   8.276%   $196.6292   $196.63   $196.65   $196.60  
  Purchase #7 $241.78   5.392%   $254.8168   $254.82   $254.80   $254.80  
  7 purchase totals = $1,055.79       $1,154.7344   $1,154.75   $1,154.75   $1,154.70