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 $61.75   11.102%   $68.6055   $68.61   $68.60   $68.60  
  Purchase #2 $130.56   10.739%   $144.5808   $144.58   $144.60   $144.60  
  Purchase #3 $141.37   5.816%   $149.5921   $149.59   $149.60   $149.60  
  Purchase #4 $246.75   7.172%   $264.4469   $264.45   $264.45   $264.40  
  Purchase #5 $124.35   9.171%   $135.7541   $135.75   $135.75   $135.80  
  Purchase #6 $39.53   5.544%   $41.7215   $41.72   $41.70   $41.70  
  Purchase #7 $215.45   7.348%   $231.2813   $231.28   $231.30   $231.30  
  7 purchase totals = $959.76       $1,035.9822   $1,035.98   $1,036.00   $1,036.00