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 $91.94   5.492%   $96.9893   $96.99   $97.00   $97.00  
  Purchase #2 $208.73   5.680%   $220.5859   $220.59   $220.60   $220.60  
  Purchase #3 $111.50   5.220%   $117.3203   $117.32   $117.30   $117.30  
  Purchase #4 $175.31   5.561%   $185.059   $185.06   $185.05   $185.10  
  Purchase #5 $9.43   3.874%   $9.7953   $9.80   $9.80   $9.80  
  Purchase #6 $159.35   5.454%   $168.0409   $168.04   $168.05   $168.00  
  Purchase #7 $142.56   13.760%   $162.1763   $162.18   $162.20   $162.20  
  7 purchase totals = $898.82       $959.9670   $959.98   $960.00   $960.00