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 $52.98   10.573%   $58.5816   $58.58   $58.60   $58.60  
  Purchase #2 $245.46   12.323%   $275.708   $275.71   $275.70   $275.70  
  Purchase #3 $248.97   10.721%   $275.6621   $275.66   $275.65   $275.70  
  Purchase #4 $153.57   11.260%   $170.862   $170.86   $170.85   $170.90  
  Purchase #5 $125.88   12.426%   $141.5218   $141.52   $141.50   $141.50  
  Purchase #6 $65.49   12.213%   $73.4883   $73.49   $73.50   $73.50  
  Purchase #7 $36.48   3.359%   $37.7054   $37.71   $37.70   $37.70  
  7 purchase totals = $928.83       $1,033.5292   $1,033.53   $1,033.50   $1,033.60