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 $54.73   13.234%   $61.973   $61.97   $61.95   $62.00  
  Purchase #2 $192.44   6.757%   $205.4432   $205.44   $205.45   $205.40  
  Purchase #3 $216.38   5.809%   $228.9495   $228.95   $228.95   $228.90  
  Purchase #4 $155.86   4.300%   $162.562   $162.56   $162.55   $162.60  
  Purchase #5 $242.72   5.784%   $256.7589   $256.76   $256.75   $256.80  
  Purchase #6 $130.65   7.807%   $140.8498   $140.85   $140.85   $140.80  
  Purchase #7 $132.41   10.864%   $146.795   $146.80   $146.80   $146.80  
  7 purchase totals = $1,125.19       $1,203.3314   $1,203.33   $1,203.30   $1,203.30