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 $130.39   3.205%   $134.569   $134.57   $134.55   $134.60  
  Purchase #2 $112.96   5.527%   $119.2033   $119.20   $119.20   $119.20  
  Purchase #3 $92.34   7.229%   $99.0153   $99.02   $99.00   $99.00  
  Purchase #4 $88.49   8.123%   $95.678   $95.68   $95.70   $95.70  
  Purchase #5 $238.63   6.302%   $253.6685   $253.67   $253.65   $253.70  
  Purchase #6 $161.76   6.465%   $172.2178   $172.22   $172.20   $172.20  
  Purchase #7 $239.37   5.483%   $252.4947   $252.49   $252.50   $252.50  
  7 purchase totals = $1,063.94       $1,126.8466   $1,126.85   $1,126.80   $1,126.90