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 $88.50   5.376%   $93.2578   $93.26   $93.25   $93.30  
  Purchase #2 $176.90   13.298%   $200.4242   $200.42   $200.40   $200.40  
  Purchase #3 $206.59   3.567%   $213.9591   $213.96   $213.95   $214.00  
  Purchase #4 $53.67   4.818%   $56.2558   $56.26   $56.25   $56.30  
  Purchase #5 $61.72   8.155%   $66.7533   $66.75   $66.75   $66.80  
  Purchase #6 $212.87   3.439%   $220.1906   $220.19   $220.20   $220.20  
  Purchase #7 $200.68   6.736%   $214.1978   $214.20   $214.20   $214.20  
  7 purchase totals = $1,000.93       $1,065.0386   $1,065.04   $1,065.00   $1,065.20