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 $94.88   7.114%   $101.6298   $101.63   $101.65   $101.60  
  Purchase #2 $40.42   7.521%   $43.46   $43.46   $43.45   $43.50  
  Purchase #3 $96.94   8.360%   $105.0442   $105.04   $105.05   $105.00  
  Purchase #4 $167.59   4.859%   $175.7332   $175.73   $175.75   $175.70  
  Purchase #5 $53.52   12.800%   $60.3706   $60.37   $60.35   $60.40  
  Purchase #6 $107.97   9.658%   $118.3977   $118.40   $118.40   $118.40  
  Purchase #7 $19.49   4.718%   $20.4095   $20.41   $20.40   $20.40  
  7 purchase totals = $580.81       $625.0450   $625.04   $625.05   $625.00