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 $114.98   3.597%   $119.1158   $119.12   $119.10   $119.10  
  Purchase #2 $43.96   6.121%   $46.6508   $46.65   $46.65   $46.70  
  Purchase #3 $82.41   7.351%   $88.468   $88.47   $88.45   $88.50  
  Purchase #4 $153.25   8.158%   $165.7521   $165.75   $165.75   $165.80  
  Purchase #5 $51.53   4.792%   $53.9993   $54.00   $54.00   $54.00  
  Purchase #6 $183.67   6.824%   $196.2036   $196.20   $196.20   $196.20  
  Purchase #7 $117.29   13.844%   $133.5276   $133.53   $133.55   $133.50  
  7 purchase totals = $747.09       $803.7172   $803.72   $803.70   $803.80