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 $86.98   7.219%   $93.2591   $93.26   $93.25   $93.30  
  Purchase #2 $106.54   4.701%   $111.5484   $111.55   $111.55   $111.50  
  Purchase #3 $231.46   10.816%   $256.4947   $256.49   $256.50   $256.50  
  Purchase #4 $89.41   7.371%   $96.0004   $96.00   $96.00   $96.00  
  Purchase #5 $118.96   5.395%   $125.3779   $125.38   $125.40   $125.40  
  Purchase #6 $111.37   9.614%   $122.0771   $122.08   $122.10   $122.10  
  Purchase #7 $188.72   10.873%   $209.2395   $209.24   $209.25   $209.20  
  7 purchase totals = $933.44       $1,013.9971   $1,014.00   $1,014.05   $1,014.00