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 $95.33   3.705%   $98.862   $98.86   $98.85   $98.90  
  Purchase #2 $207.94   9.784%   $228.2848   $228.28   $228.30   $228.30  
  Purchase #3 $59.86   9.686%   $65.658   $65.66   $65.65   $65.70  
  Purchase #4 $174.33   7.521%   $187.4414   $187.44   $187.45   $187.40  
  Purchase #5 $131.91   11.451%   $147.015   $147.02   $147.00   $147.00  
  Purchase #6 $195.72   9.330%   $213.9807   $213.98   $214.00   $214.00  
  Purchase #7 $242.26   13.352%   $274.6066   $274.61   $274.60   $274.60  
  7 purchase totals = $1,107.35       $1,215.8485   $1,215.85   $1,215.85   $1,215.90