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 $33.95   4.623%   $35.5195   $35.52   $35.50   $35.50  
  Purchase #2 $22.48   11.102%   $24.9757   $24.98   $25.00   $25.00  
  Purchase #3 $164.41   8.201%   $177.8933   $177.89   $177.90   $177.90  
  Purchase #4 $214.32   9.575%   $234.8411   $234.84   $234.85   $234.80  
  Purchase #5 $178.60   11.488%   $199.1176   $199.12   $199.10   $199.10  
  Purchase #6 $213.64   3.173%   $220.4188   $220.42   $220.40   $220.40  
  Purchase #7 $120.78   10.849%   $133.8834   $133.88   $133.90   $133.90  
  7 purchase totals = $948.18       $1,026.6494   $1,026.65   $1,026.65   $1,026.60