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 $214.66   6.452%   $228.5099   $228.51   $228.50   $228.50  
  Purchase #2 $241.48   9.334%   $264.0197   $264.02   $264.00   $264.00  
  Purchase #3 $208.64   11.310%   $232.2372   $232.24   $232.25   $232.20  
  Purchase #4 $209.52   9.164%   $228.7204   $228.72   $228.70   $228.70  
  Purchase #5 $58.41   3.319%   $60.3486   $60.35   $60.35   $60.30  
  Purchase #6 $146.78   4.843%   $153.8886   $153.89   $153.90   $153.90  
  Purchase #7 $83.68   12.741%   $94.3417   $94.34   $94.35   $94.30  
  7 purchase totals = $1,163.17       $1,262.0661   $1,262.07   $1,262.05   $1,261.90