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 $132.26   9.861%   $145.3022   $145.30   $145.30   $145.30  
  Purchase #2 $240.57   8.643%   $261.3625   $261.36   $261.35   $261.40  
  Purchase #3 $220.71   6.810%   $235.7404   $235.74   $235.75   $235.70  
  Purchase #4 $172.79   4.114%   $179.8986   $179.90   $179.90   $179.90  
  Purchase #5 $125.58   10.840%   $139.1929   $139.19   $139.20   $139.20  
  Purchase #6 $111.82   10.236%   $123.2659   $123.27   $123.25   $123.30  
  Purchase #7 $104.29   12.732%   $117.5682   $117.57   $117.55   $117.60  
  7 purchase totals = $1,108.02       $1,202.3307   $1,202.33   $1,202.30   $1,202.40