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 $187.85   5.111%   $197.451   $197.45   $197.45   $197.50  
  Purchase #2 $166.48   5.560%   $175.7363   $175.74   $175.75   $175.70  
  Purchase #3 $126.50   13.290%   $143.3119   $143.31   $143.30   $143.30  
  Purchase #4 $52.59   9.712%   $57.6975   $57.70   $57.70   $57.70  
  Purchase #5 $70.99   12.133%   $79.6032   $79.60   $79.60   $79.60  
  Purchase #6 $118.29   5.622%   $124.9403   $124.94   $124.95   $124.90  
  Purchase #7 $102.64   13.661%   $116.6617   $116.66   $116.65   $116.70  
  7 purchase totals = $825.34       $895.4019   $895.40   $895.40   $895.40