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 $58.36   5.653%   $61.6591   $61.66   $61.65   $61.70  
  Purchase #2 $87.61   9.470%   $95.9067   $95.91   $95.90   $95.90  
  Purchase #3 $163.30   8.648%   $177.4222   $177.42   $177.40   $177.40  
  Purchase #4 $136.40   5.283%   $143.606   $143.61   $143.60   $143.60  
  Purchase #5 $237.27   5.368%   $250.0067   $250.01   $250.00   $250.00  
  Purchase #6 $245.52   9.199%   $268.1054   $268.11   $268.10   $268.10  
  Purchase #7 $195.29   11.287%   $217.3324   $217.33   $217.35   $217.30  
  7 purchase totals = $1,123.75       $1,214.0385   $1,214.05   $1,214.00   $1,214.00