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 $62.44   9.768%   $68.5391   $68.54   $68.55   $68.50  
  Purchase #2 $244.52   9.368%   $267.4266   $267.43   $267.45   $267.40  
  Purchase #3 $204.42   11.367%   $227.6564   $227.66   $227.65   $227.70  
  Purchase #4 $236.61   9.492%   $259.069   $259.07   $259.05   $259.10  
  Purchase #5 $105.90   8.859%   $115.2817   $115.28   $115.30   $115.30  
  Purchase #6 $210.28   7.206%   $225.4328   $225.43   $225.45   $225.40  
  Purchase #7 $200.82   9.821%   $220.5425   $220.54   $220.55   $220.50  
  7 purchase totals = $1,264.99       $1,383.9481   $1,383.95   $1,384.00   $1,383.90