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 $90.60   4.808%   $94.956   $94.96   $94.95   $95.00  
  Purchase #2 $104.67   11.776%   $116.9959   $117.00   $117.00   $117.00  
  Purchase #3 $118.46   5.848%   $125.3875   $125.39   $125.40   $125.40  
  Purchase #4 $241.60   11.822%   $270.162   $270.16   $270.15   $270.20  
  Purchase #5 $43.81   12.175%   $49.1439   $49.14   $49.15   $49.10  
  Purchase #6 $237.79   10.645%   $263.1027   $263.10   $263.10   $263.10  
  Purchase #7 $181.81   5.747%   $192.2586   $192.26   $192.25   $192.30  
  7 purchase totals = $1,018.74       $1,112.0066   $1,112.01   $1,112.00   $1,112.10