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 $86.67   9.650%   $95.0337   $95.03   $95.05   $95.00  
  Purchase #2 $235.45   8.154%   $254.6486   $254.65   $254.65   $254.60  
  Purchase #3 $41.85   5.446%   $44.1292   $44.13   $44.15   $44.10  
  Purchase #4 $150.84   12.776%   $170.1113   $170.11   $170.10   $170.10  
  Purchase #5 $242.54   4.753%   $254.0679   $254.07   $254.05   $254.10  
  Purchase #6 $44.31   6.612%   $47.2398   $47.24   $47.25   $47.20  
  Purchase #7 $46.47   5.426%   $48.9915   $48.99   $49.00   $49.00  
  7 purchase totals = $848.13       $914.2220   $914.22   $914.25   $914.10