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 $77.90   7.522%   $83.7596   $83.76   $83.75   $83.80  
  Purchase #2 $230.61   7.475%   $247.8481   $247.85   $247.85   $247.80  
  Purchase #3 $24.62   6.565%   $26.2363   $26.24   $26.25   $26.20  
  Purchase #4 $240.63   13.442%   $272.9755   $272.98   $273.00   $273.00  
  Purchase #5 $56.91   12.204%   $63.8553   $63.86   $63.85   $63.90  
  Purchase #6 $154.58   7.799%   $166.6357   $166.64   $166.65   $166.60  
  Purchase #7 $200.30   5.340%   $210.996   $211.00   $211.00   $211.00  
  7 purchase totals = $985.55       $1,072.3065   $1,072.33   $1,072.35   $1,072.30