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 $61.72   3.259%   $63.7315   $63.73   $63.75   $63.70  
  Purchase #2 $63.73   11.501%   $71.0596   $71.06   $71.05   $71.10  
  Purchase #3 $171.66   12.453%   $193.0368   $193.04   $193.05   $193.00  
  Purchase #4 $211.47   9.701%   $231.9847   $231.98   $232.00   $232.00  
  Purchase #5 $153.43   6.195%   $162.935   $162.94   $162.95   $162.90  
  Purchase #6 $12.87   12.448%   $14.4721   $14.47   $14.45   $14.50  
  Purchase #7 $243.38   13.814%   $277.0005   $277.00   $277.00   $277.00  
  7 purchase totals = $918.26       $1,014.2202   $1,014.22   $1,014.25   $1,014.20