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 $198.44   5.765%   $209.8801   $209.88   $209.90   $209.90  
  Purchase #2 $241.51   4.590%   $252.5953   $252.60   $252.60   $252.60  
  Purchase #3 $54.40   5.591%   $57.4415   $57.44   $57.45   $57.40  
  Purchase #4 $180.93   4.630%   $189.3071   $189.31   $189.30   $189.30  
  Purchase #5 $16.31   9.486%   $17.8572   $17.86   $17.85   $17.90  
  Purchase #6 $187.92   12.672%   $211.7332   $211.73   $211.75   $211.70  
  Purchase #7 $216.90   4.511%   $226.6844   $226.68   $226.70   $226.70  
  7 purchase totals = $1,096.41       $1,165.4988   $1,165.50   $1,165.55   $1,165.50