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 $72.81   4.858%   $76.3471   $76.35   $76.35   $76.30  
  Purchase #2 $174.64   9.121%   $190.5689   $190.57   $190.55   $190.60  
  Purchase #3 $146.71   5.380%   $154.603   $154.60   $154.60   $154.60  
  Purchase #4 $226.47   11.153%   $251.7282   $251.73   $251.75   $251.70  
  Purchase #5 $184.52   9.849%   $202.6934   $202.69   $202.70   $202.70  
  Purchase #6 $105.86   10.733%   $117.222   $117.22   $117.20   $117.20  
  Purchase #7 $162.43   10.395%   $179.3146   $179.31   $179.30   $179.30  
  7 purchase totals = $1,073.44       $1,172.4772   $1,172.47   $1,172.45   $1,172.40