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 $183.34   6.864%   $195.9245   $195.92   $195.90   $195.90  
  Purchase #2 $171.47   11.765%   $191.6434   $191.64   $191.65   $191.60  
  Purchase #3 $104.97   6.480%   $111.7721   $111.77   $111.75   $111.80  
  Purchase #4 $216.94   5.790%   $229.5008   $229.50   $229.50   $229.50  
  Purchase #5 $250.96   10.636%   $277.6521   $277.65   $277.65   $277.70  
  Purchase #6 $126.89   6.832%   $135.5591   $135.56   $135.55   $135.60  
  Purchase #7 $56.74   11.619%   $63.3326   $63.33   $63.35   $63.30  
  7 purchase totals = $1,111.31       $1,205.3846   $1,205.37   $1,205.35   $1,205.40