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 $216.87   9.673%   $237.8478   $237.85   $237.85   $237.80  
  Purchase #2 $65.36   6.558%   $69.6463   $69.65   $69.65   $69.60  
  Purchase #3 $160.87   4.428%   $167.9933   $167.99   $168.00   $168.00  
  Purchase #4 $164.62   13.755%   $187.2635   $187.26   $187.25   $187.30  
  Purchase #5 $180.89   7.571%   $194.5852   $194.59   $194.60   $194.60  
  Purchase #6 $236.91   4.473%   $247.507   $247.51   $247.50   $247.50  
  Purchase #7 $104.28   7.343%   $111.9373   $111.94   $111.95   $111.90  
  7 purchase totals = $1,129.80       $1,216.7804   $1,216.79   $1,216.80   $1,216.70