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 $92.68   3.539%   $95.9599   $95.96   $95.95   $96.00  
  Purchase #2 $176.95   8.294%   $191.6262   $191.63   $191.65   $191.60  
  Purchase #3 $133.78   3.173%   $138.0248   $138.02   $138.00   $138.00  
  Purchase #4 $9.72   6.131%   $10.3159   $10.32   $10.30   $10.30  
  Purchase #5 $176.96   8.205%   $191.4796   $191.48   $191.50   $191.50  
  Purchase #6 $130.51   3.834%   $135.5138   $135.51   $135.50   $135.50  
  Purchase #7 $31.76   5.258%   $33.4299   $33.43   $33.45   $33.40  
  7 purchase totals = $752.36       $796.3501   $796.35   $796.35   $796.30