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 $78.46   8.250%   $84.933   $84.93   $84.95   $84.90  
  Purchase #2 $152.68   9.284%   $166.8548   $166.85   $166.85   $166.90  
  Purchase #3 $63.54   11.316%   $70.7302   $70.73   $70.75   $70.70  
  Purchase #4 $244.59   7.764%   $263.58   $263.58   $263.60   $263.60  
  Purchase #5 $56.77   3.818%   $58.9375   $58.94   $58.95   $58.90  
  Purchase #6 $224.68   8.774%   $244.3934   $244.39   $244.40   $244.40  
  Purchase #7 $205.84   9.795%   $226.002   $226.00   $226.00   $226.00  
  7 purchase totals = $1,026.56       $1,115.4309   $1,115.42   $1,115.50   $1,115.40