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 $49.43   5.578%   $52.1872   $52.19   $52.20   $52.20  
  Purchase #2 $236.27   6.199%   $250.9164   $250.92   $250.90   $250.90  
  Purchase #3 $31.83   10.152%   $35.0614   $35.06   $35.05   $35.10  
  Purchase #4 $26.92   10.796%   $29.8263   $29.83   $29.85   $29.80  
  Purchase #5 $186.53   10.807%   $206.6883   $206.69   $206.70   $206.70  
  Purchase #6 $161.26   7.186%   $172.8481   $172.85   $172.85   $172.80  
  Purchase #7 $242.49   10.235%   $267.3089   $267.31   $267.30   $267.30  
  7 purchase totals = $934.73       $1,014.8366   $1,014.85   $1,014.85   $1,014.80