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 $57.60   7.753%   $62.0657   $62.07   $62.05   $62.10  
  Purchase #2 $104.41   5.638%   $110.2966   $110.30   $110.30   $110.30  
  Purchase #3 $14.37   9.712%   $15.7656   $15.77   $15.75   $15.80  
  Purchase #4 $113.70   5.866%   $120.3696   $120.37   $120.35   $120.40  
  Purchase #5 $67.94   10.483%   $75.0622   $75.06   $75.05   $75.10  
  Purchase #6 $148.91   7.210%   $159.6464   $159.65   $159.65   $159.60  
  Purchase #7 $188.96   5.111%   $198.6177   $198.62   $198.60   $198.60  
  7 purchase totals = $695.89       $741.8238   $741.84   $741.75   $741.90