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 $60.64   13.795%   $69.0053   $69.01   $69.00   $69.00  
  Purchase #2 $220.84   5.687%   $233.3992   $233.40   $233.40   $233.40  
  Purchase #3 $228.98   11.849%   $256.1118   $256.11   $256.10   $256.10  
  Purchase #4 $128.80   7.179%   $138.0466   $138.05   $138.05   $138.00  
  Purchase #5 $95.80   7.164%   $102.6631   $102.66   $102.65   $102.70  
  Purchase #6 $243.48   13.731%   $276.9122   $276.91   $276.90   $276.90  
  Purchase #7 $173.35   7.438%   $186.2438   $186.24   $186.25   $186.20  
  7 purchase totals = $1,151.89       $1,262.3820   $1,262.38   $1,262.35   $1,262.30