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 $87.76   7.869%   $94.6658   $94.67   $94.65   $94.70  
  Purchase #2 $82.93   6.853%   $88.6132   $88.61   $88.60   $88.60  
  Purchase #3 $211.98   3.546%   $219.4968   $219.50   $219.50   $219.50  
  Purchase #4 $68.25   4.665%   $71.4339   $71.43   $71.45   $71.40  
  Purchase #5 $64.68   12.405%   $72.7036   $72.70   $72.70   $72.70  
  Purchase #6 $208.40   8.491%   $226.0952   $226.10   $226.10   $226.10  
  Purchase #7 $165.71   9.235%   $181.0133   $181.01   $181.00   $181.00  
  7 purchase totals = $889.71       $954.0218   $954.02   $954.00   $954.00