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 $106.98   11.241%   $119.0056   $119.01   $119.00   $119.00  
  Purchase #2 $95.61   11.791%   $106.8834   $106.88   $106.90   $106.90  
  Purchase #3 $153.60   8.866%   $167.2182   $167.22   $167.20   $167.20  
  Purchase #4 $245.94   7.643%   $264.7372   $264.74   $264.75   $264.70  
  Purchase #5 $206.49   4.444%   $215.6664   $215.67   $215.65   $215.70  
  Purchase #6 $184.60   4.625%   $193.1378   $193.14   $193.15   $193.10  
  Purchase #7 $58.97   12.266%   $66.2033   $66.20   $66.20   $66.20  
  7 purchase totals = $1,052.19       $1,132.8519   $1,132.86   $1,132.85   $1,132.80