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 $96.74   5.461%   $102.023   $102.02   $102.00   $102.00  
  Purchase #2 $71.74   9.579%   $78.612   $78.61   $78.60   $78.60  
  Purchase #3 $200.53   3.802%   $208.1542   $208.15   $208.15   $208.20  
  Purchase #4 $63.72   12.471%   $71.6665   $71.67   $71.65   $71.70  
  Purchase #5 $149.25   11.560%   $166.5033   $166.50   $166.50   $166.50  
  Purchase #6 $167.64   12.545%   $188.6704   $188.67   $188.65   $188.70  
  Purchase #7 $213.84   3.169%   $220.6166   $220.62   $220.60   $220.60  
  7 purchase totals = $963.46       $1,036.2460   $1,036.24   $1,036.15   $1,036.30