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 $32.60   4.151%   $33.9532   $33.95   $33.95   $34.00  
  Purchase #2 $95.60   12.652%   $107.6953   $107.70   $107.70   $107.70  
  Purchase #3 $233.61   13.740%   $265.708   $265.71   $265.70   $265.70  
  Purchase #4 $223.76   8.590%   $242.981   $242.98   $243.00   $243.00  
  Purchase #5 $212.86   13.361%   $241.3002   $241.30   $241.30   $241.30  
  Purchase #6 $178.51   3.400%   $184.5793   $184.58   $184.60   $184.60  
  Purchase #7 $171.52   5.351%   $180.698   $180.70   $180.70   $180.70  
  7 purchase totals = $1,148.46       $1,256.9150   $1,256.92   $1,256.95   $1,257.00