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 $68.96   10.238%   $76.0201   $76.02   $76.00   $76.00  
  Purchase #2 $153.54   8.873%   $167.1636   $167.16   $167.15   $167.20  
  Purchase #3 $137.41   12.188%   $154.1575   $154.16   $154.15   $154.20  
  Purchase #4 $205.42   6.725%   $219.2345   $219.23   $219.25   $219.20  
  Purchase #5 $160.25   11.488%   $178.6595   $178.66   $178.65   $178.70  
  Purchase #6 $39.91   13.246%   $45.1965   $45.20   $45.20   $45.20  
  Purchase #7 $77.68   12.525%   $87.4094   $87.41   $87.40   $87.40  
  7 purchase totals = $843.17       $927.8411   $927.84   $927.80   $927.90