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 $66.52   4.416%   $69.4575   $69.46   $69.45   $69.50  
  Purchase #2 $90.65   10.421%   $100.0966   $100.10   $100.10   $100.10  
  Purchase #3 $202.96   6.421%   $215.9921   $215.99   $216.00   $216.00  
  Purchase #4 $87.66   6.613%   $93.457   $93.46   $93.45   $93.50  
  Purchase #5 $30.45   11.453%   $33.9374   $33.94   $33.95   $33.90  
  Purchase #6 $248.99   9.380%   $272.3453   $272.35   $272.35   $272.30  
  Purchase #7 $199.29   13.231%   $225.6581   $225.66   $225.65   $225.70  
  7 purchase totals = $926.52       $1,010.9440   $1,010.96   $1,010.95   $1,011.00