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 $113.77   10.772%   $126.0253   $126.03   $126.05   $126.00  
  Purchase #2 $204.59   7.441%   $219.8135   $219.81   $219.80   $219.80  
  Purchase #3 $25.82   13.201%   $29.2285   $29.23   $29.25   $29.20  
  Purchase #4 $248.46   6.117%   $263.6583   $263.66   $263.65   $263.70  
  Purchase #5 $25.61   3.617%   $26.5363   $26.54   $26.55   $26.50  
  Purchase #6 $91.58   5.481%   $96.5995   $96.60   $96.60   $96.60  
  Purchase #7 $182.35   3.155%   $188.1031   $188.10   $188.10   $188.10  
  7 purchase totals = $892.18       $949.9645   $949.97   $950.00   $949.90