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 $114.28   4.212%   $119.0935   $119.09   $119.10   $119.10  
  Purchase #2 $211.45   12.619%   $238.1329   $238.13   $238.15   $238.10  
  Purchase #3 $243.32   9.781%   $267.1191   $267.12   $267.10   $267.10  
  Purchase #4 $64.56   10.822%   $71.5467   $71.55   $71.55   $71.50  
  Purchase #5 $241.33   7.143%   $258.5682   $258.57   $258.55   $258.60  
  Purchase #6 $77.96   5.421%   $82.1862   $82.19   $82.20   $82.20  
  Purchase #7 $201.40   4.286%   $210.032   $210.03   $210.05   $210.00  
  7 purchase totals = $1,154.30       $1,246.6786   $1,246.68   $1,246.70   $1,246.60