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 $190.27   11.408%   $211.976   $211.98   $212.00   $212.00  
  Purchase #2 $180.97   12.349%   $203.318   $203.32   $203.30   $203.30  
  Purchase #3 $72.88   11.319%   $81.1293   $81.13   $81.15   $81.10  
  Purchase #4 $192.39   6.284%   $204.4798   $204.48   $204.50   $204.50  
  Purchase #5 $77.61   5.852%   $82.1517   $82.15   $82.15   $82.20  
  Purchase #6 $14.27   3.174%   $14.7229   $14.72   $14.70   $14.70  
  Purchase #7 $188.89   3.623%   $195.7335   $195.73   $195.75   $195.70  
  7 purchase totals = $917.28       $993.5112   $993.51   $993.55   $993.50