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 $60.34   11.871%   $67.503   $67.50   $67.50   $67.50  
  Purchase #2 $217.51   5.631%   $229.758   $229.76   $229.75   $229.80  
  Purchase #3 $87.55   9.589%   $95.9452   $95.95   $95.95   $95.90  
  Purchase #4 $21.76   10.419%   $24.0272   $24.03   $24.05   $24.00  
  Purchase #5 $203.52   12.472%   $228.903   $228.90   $228.90   $228.90  
  Purchase #6 $192.51   10.410%   $212.5503   $212.55   $212.55   $212.60  
  Purchase #7 $34.89   6.271%   $37.078   $37.08   $37.10   $37.10  
  7 purchase totals = $818.08       $895.7647   $895.77   $895.80   $895.80