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 $87.37   8.710%   $94.9799   $94.98   $95.00   $95.00  
  Purchase #2 $27.41   13.764%   $31.1827   $31.18   $31.20   $31.20  
  Purchase #3 $20.50   9.335%   $22.4137   $22.41   $22.40   $22.40  
  Purchase #4 $86.28   8.313%   $93.4525   $93.45   $93.45   $93.50  
  Purchase #5 $125.46   13.805%   $142.7798   $142.78   $142.80   $142.80  
  Purchase #6 $120.95   9.131%   $131.9939   $131.99   $132.00   $132.00  
  Purchase #7 $49.56   7.699%   $53.3756   $53.38   $53.40   $53.40  
  7 purchase totals = $517.53       $570.1781   $570.17   $570.25   $570.30