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 $57.55   7.232%   $61.712   $61.71   $61.70   $61.70  
  Purchase #2 $189.28   3.122%   $195.1893   $195.19   $195.20   $195.20  
  Purchase #3 $39.93   13.215%   $45.2067   $45.21   $45.20   $45.20  
  Purchase #4 $42.42   3.621%   $43.956   $43.96   $43.95   $44.00  
  Purchase #5 $169.76   10.438%   $187.4795   $187.48   $187.50   $187.50  
  Purchase #6 $106.84   9.161%   $116.6276   $116.63   $116.65   $116.60  
  Purchase #7 $103.62   4.709%   $108.4995   $108.50   $108.50   $108.50  
  7 purchase totals = $709.40       $758.6706   $758.68   $758.70   $758.70