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 $59.73   9.150%   $65.1953   $65.20   $65.20   $65.20  
  Purchase #2 $88.80   8.713%   $96.5371   $96.54   $96.55   $96.50  
  Purchase #3 $232.75   11.228%   $258.8832   $258.88   $258.90   $258.90  
  Purchase #4 $235.83   3.552%   $244.2067   $244.21   $244.20   $244.20  
  Purchase #5 $193.39   4.322%   $201.7483   $201.75   $201.75   $201.70  
  Purchase #6 $231.83   11.390%   $258.2354   $258.24   $258.25   $258.20  
  Purchase #7 $40.67   8.258%   $44.0285   $44.03   $44.05   $44.00  
  7 purchase totals = $1,083.00       $1,168.8345   $1,168.85   $1,168.90   $1,168.70