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 $69.91   8.276%   $75.6958   $75.70   $75.70   $75.70  
  Purchase #2 $239.80   5.279%   $252.459   $252.46   $252.45   $252.50  
  Purchase #3 $111.92   5.366%   $117.9256   $117.93   $117.95   $117.90  
  Purchase #4 $175.97   7.654%   $189.4387   $189.44   $189.45   $189.40  
  Purchase #5 $169.80   12.648%   $191.2763   $191.28   $191.30   $191.30  
  Purchase #6 $196.26   10.213%   $216.304   $216.30   $216.30   $216.30  
  Purchase #7 $11.52   7.723%   $12.4097   $12.41   $12.40   $12.40  
  7 purchase totals = $975.18       $1,055.5091   $1,055.52   $1,055.55   $1,055.50