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 $162.65   7.356%   $174.6145   $174.61   $174.60   $174.60  
  Purchase #2 $150.99   3.190%   $155.8066   $155.81   $155.80   $155.80  
  Purchase #3 $80.62   9.596%   $88.3563   $88.36   $88.35   $88.40  
  Purchase #4 $235.93   11.311%   $262.616   $262.62   $262.60   $262.60  
  Purchase #5 $115.99   3.127%   $119.617   $119.62   $119.60   $119.60  
  Purchase #6 $133.82   13.561%   $151.9673   $151.97   $151.95   $152.00  
  Purchase #7 $129.85   6.326%   $138.0643   $138.06   $138.05   $138.10  
  7 purchase totals = $1,009.85       $1,091.0420   $1,091.05   $1,090.95   $1,091.10