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 $60.61   13.863%   $69.0124   $69.01   $69.00   $69.00  
  Purchase #2 $126.59   4.524%   $132.3169   $132.32   $132.30   $132.30  
  Purchase #3 $62.80   12.628%   $70.7304   $70.73   $70.75   $70.70  
  Purchase #4 $156.85   13.781%   $178.4655   $178.47   $178.45   $178.50  
  Purchase #5 $228.74   6.298%   $243.146   $243.15   $243.15   $243.10  
  Purchase #6 $67.32   11.705%   $75.1998   $75.20   $75.20   $75.20  
  Purchase #7 $89.70   3.733%   $93.0485   $93.05   $93.05   $93.00  
  7 purchase totals = $792.61       $861.9195   $861.93   $861.90   $861.80