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 $85.28   12.422%   $95.8735   $95.87   $95.85   $95.90  
  Purchase #2 $91.84   3.588%   $95.1352   $95.14   $95.15   $95.10  
  Purchase #3 $117.80   13.757%   $134.0057   $134.01   $134.00   $134.00  
  Purchase #4 $54.29   10.103%   $59.7749   $59.77   $59.75   $59.80  
  Purchase #5 $65.87   3.281%   $68.0312   $68.03   $68.05   $68.00  
  Purchase #6 $237.32   9.171%   $259.0846   $259.08   $259.10   $259.10  
  Purchase #7 $62.87   3.525%   $65.0862   $65.09   $65.10   $65.10  
  7 purchase totals = $715.27       $776.9913   $776.99   $777.00   $777.00