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 $90.47   5.106%   $95.0894   $95.09   $95.10   $95.10  
  Purchase #2 $136.35   12.547%   $153.4578   $153.46   $153.45   $153.50  
  Purchase #3 $228.60   6.725%   $243.9734   $243.97   $243.95   $244.00  
  Purchase #4 $144.60   12.116%   $162.1197   $162.12   $162.10   $162.10  
  Purchase #5 $110.27   12.829%   $124.4165   $124.42   $124.40   $124.40  
  Purchase #6 $17.83   9.304%   $19.4889   $19.49   $19.50   $19.50  
  Purchase #7 $74.85   3.467%   $77.445   $77.45   $77.45   $77.40  
  7 purchase totals = $802.97       $875.9907   $876.00   $875.95   $876.00