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 $60.85   3.546%   $63.0077   $63.01   $63.00   $63.00  
  Purchase #2 $79.84   3.757%   $82.8396   $82.84   $82.85   $82.80  
  Purchase #3 $201.90   12.217%   $226.5661   $226.57   $226.55   $226.60  
  Purchase #4 $222.35   6.175%   $236.0801   $236.08   $236.10   $236.10  
  Purchase #5 $132.86   6.361%   $141.3112   $141.31   $141.30   $141.30  
  Purchase #6 $140.66   3.372%   $145.4031   $145.40   $145.40   $145.40  
  Purchase #7 $244.39   13.706%   $277.8861   $277.89   $277.90   $277.90  
  7 purchase totals = $1,082.85       $1,173.0939   $1,173.10   $1,173.10   $1,173.10