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 $88.99   6.314%   $94.6088   $94.61   $94.60   $94.60  
  Purchase #2 $169.86   12.426%   $190.9668   $190.97   $190.95   $191.00  
  Purchase #3 $227.60   10.618%   $251.7666   $251.77   $251.75   $251.80  
  Purchase #4 $109.55   13.846%   $124.7183   $124.72   $124.70   $124.70  
  Purchase #5 $169.78   9.705%   $186.2571   $186.26   $186.25   $186.30  
  Purchase #6 $67.92   6.261%   $72.1725   $72.17   $72.15   $72.20  
  Purchase #7 $174.31   11.444%   $194.258   $194.26   $194.25   $194.30  
  7 purchase totals = $1,008.01       $1,114.7481   $1,114.76   $1,114.65   $1,114.90