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 $131.59   8.279%   $142.4843   $142.48   $142.50   $142.50  
  Purchase #2 $23.77   5.431%   $25.0609   $25.06   $25.05   $25.10  
  Purchase #3 $64.99   11.254%   $72.304   $72.30   $72.30   $72.30  
  Purchase #4 $106.97   9.819%   $117.4734   $117.47   $117.45   $117.50  
  Purchase #5 $30.55   5.292%   $32.1667   $32.17   $32.15   $32.20  
  Purchase #6 $120.92   10.154%   $133.1982   $133.20   $133.20   $133.20  
  Purchase #7 $193.25   9.282%   $211.1875   $211.19   $211.20   $211.20  
  7 purchase totals = $672.04       $733.8750   $733.87   $733.85   $734.00