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 $232.42   12.699%   $261.935   $261.94   $261.95   $261.90  
  Purchase #2 $193.38   12.568%   $217.684   $217.68   $217.70   $217.70  
  Purchase #3 $225.53   7.865%   $243.2679   $243.27   $243.25   $243.30  
  Purchase #4 $211.27   5.860%   $223.6504   $223.65   $223.65   $223.70  
  Purchase #5 $127.33   4.626%   $133.2203   $133.22   $133.20   $133.20  
  Purchase #6 $203.75   7.803%   $219.6486   $219.65   $219.65   $219.60  
  Purchase #7 $219.45   5.353%   $231.1972   $231.20   $231.20   $231.20  
  7 purchase totals = $1,413.13       $1,530.6034   $1,530.61   $1,530.60   $1,530.60