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 $60.46   13.556%   $68.656   $68.66   $68.65   $68.70  
  Purchase #2 $212.63   13.742%   $241.8496   $241.85   $241.85   $241.80  
  Purchase #3 $10.64   5.839%   $11.2613   $11.26   $11.25   $11.30  
  Purchase #4 $93.70   13.779%   $106.6109   $106.61   $106.60   $106.60  
  Purchase #5 $53.60   4.195%   $55.8485   $55.85   $55.85   $55.80  
  Purchase #6 $223.31   9.818%   $245.2346   $245.23   $245.25   $245.20  
  Purchase #7 $47.99   6.262%   $50.9951   $51.00   $51.00   $51.00  
  7 purchase totals = $702.33       $780.4560   $780.46   $780.45   $780.40