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 $186.99   5.319%   $196.936   $196.94   $196.95   $196.90  
  Purchase #2 $216.84   3.610%   $224.6679   $224.67   $224.65   $224.70  
  Purchase #3 $178.80   9.669%   $196.0882   $196.09   $196.10   $196.10  
  Purchase #4 $68.40   7.608%   $73.6039   $73.60   $73.60   $73.60  
  Purchase #5 $154.35   4.828%   $161.802   $161.80   $161.80   $161.80  
  Purchase #6 $164.90   9.443%   $180.4715   $180.47   $180.45   $180.50  
  Purchase #7 $158.55   7.837%   $170.9756   $170.98   $171.00   $171.00  
  7 purchase totals = $1,128.83       $1,204.5451   $1,204.55   $1,204.55   $1,204.60