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 $72.43   4.726%   $75.853   $75.85   $75.85   $75.90  
  Purchase #2 $99.44   4.115%   $103.532   $103.53   $103.55   $103.50  
  Purchase #3 $134.87   9.506%   $147.6907   $147.69   $147.70   $147.70  
  Purchase #4 $222.51   7.413%   $239.0047   $239.00   $239.00   $239.00  
  Purchase #5 $191.75   7.804%   $206.7142   $206.71   $206.70   $206.70  
  Purchase #6 $34.64   5.675%   $36.6058   $36.61   $36.60   $36.60  
  Purchase #7 $87.69   7.219%   $94.0203   $94.02   $94.00   $94.00  
  7 purchase totals = $843.33       $903.4207   $903.41   $903.40   $903.40