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 $57.88   5.298%   $60.9465   $60.95   $60.95   $60.90  
  Purchase #2 $93.89   11.669%   $104.846   $104.85   $104.85   $104.80  
  Purchase #3 $194.44   8.701%   $211.3582   $211.36   $211.35   $211.40  
  Purchase #4 $186.66   10.401%   $206.0745   $206.07   $206.05   $206.10  
  Purchase #5 $243.35   5.280%   $256.1989   $256.20   $256.20   $256.20  
  Purchase #6 $174.27   9.152%   $190.2192   $190.22   $190.20   $190.20  
  Purchase #7 $225.60   5.526%   $238.0667   $238.07   $238.05   $238.10  
  7 purchase totals = $1,176.09       $1,267.7100   $1,267.72   $1,267.65   $1,267.70