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 $169.66   6.691%   $181.012   $181.01   $181.00   $181.00  
  Purchase #2 $92.62   3.652%   $96.0025   $96.00   $96.00   $96.00  
  Purchase #3 $130.92   9.483%   $143.3351   $143.34   $143.35   $143.30  
  Purchase #4 $248.55   8.143%   $268.7894   $268.79   $268.80   $268.80  
  Purchase #5 $175.75   11.529%   $196.0122   $196.01   $196.00   $196.00  
  Purchase #6 $44.89   3.328%   $46.3839   $46.38   $46.40   $46.40  
  Purchase #7 $155.66   13.593%   $176.8189   $176.82   $176.80   $176.80  
  7 purchase totals = $1,018.05       $1,108.3540   $1,108.35   $1,108.35   $1,108.30