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 $217.47   6.817%   $232.2949   $232.29   $232.30   $232.30  
  Purchase #2 $97.52   8.330%   $105.6434   $105.64   $105.65   $105.60  
  Purchase #3 $225.76   9.252%   $246.6473   $246.65   $246.65   $246.60  
  Purchase #4 $16.60   7.245%   $17.8027   $17.80   $17.80   $17.80  
  Purchase #5 $167.39   12.832%   $188.8695   $188.87   $188.85   $188.90  
  Purchase #6 $201.95   5.796%   $213.655   $213.66   $213.65   $213.70  
  Purchase #7 $169.26   13.609%   $192.2946   $192.29   $192.30   $192.30  
  7 purchase totals = $1,095.95       $1,197.2074   $1,197.20   $1,197.20   $1,197.20