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 $184.83   8.847%   $201.1819   $201.18   $201.20   $201.20  
  Purchase #2 $46.65   11.472%   $52.0017   $52.00   $52.00   $52.00  
  Purchase #3 $224.46   5.361%   $236.4933   $236.49   $236.50   $236.50  
  Purchase #4 $59.89   3.835%   $62.1868   $62.19   $62.20   $62.20  
  Purchase #5 $172.80   13.253%   $195.7012   $195.70   $195.70   $195.70  
  Purchase #6 $246.74   8.764%   $268.3643   $268.36   $268.35   $268.40  
  Purchase #7 $123.89   9.748%   $135.9668   $135.97   $135.95   $136.00  
  7 purchase totals = $1,059.26       $1,151.8960   $1,151.89   $1,151.90   $1,152.00