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 $162.89   8.347%   $176.4864   $176.49   $176.50   $176.50  
  Purchase #2 $180.82   7.703%   $194.7486   $194.75   $194.75   $194.70  
  Purchase #3 $53.99   12.339%   $60.6518   $60.65   $60.65   $60.70  
  Purchase #4 $213.48   4.605%   $223.3108   $223.31   $223.30   $223.30  
  Purchase #5 $57.82   8.314%   $62.6272   $62.63   $62.65   $62.60  
  Purchase #6 $89.65   7.479%   $96.3549   $96.35   $96.35   $96.40  
  Purchase #7 $232.87   9.760%   $255.5981   $255.60   $255.60   $255.60  
  7 purchase totals = $991.52       $1,069.7778   $1,069.78   $1,069.80   $1,069.80