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 $23.67   9.851%   $26.0017   $26.00   $26.00   $26.00  
  Purchase #2 $163.57   9.662%   $179.3741   $179.37   $179.35   $179.40  
  Purchase #3 $121.50   3.166%   $125.3467   $125.35   $125.35   $125.30  
  Purchase #4 $110.73   8.137%   $119.7401   $119.74   $119.75   $119.70  
  Purchase #5 $41.72   11.790%   $46.6388   $46.64   $46.65   $46.60  
  Purchase #6 $151.69   11.607%   $169.2967   $169.30   $169.30   $169.30  
  Purchase #7 $232.92   7.254%   $249.816   $249.82   $249.80   $249.80  
  7 purchase totals = $845.80       $916.2141   $916.22   $916.20   $916.10