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 $64.90   6.837%   $69.3372   $69.34   $69.35   $69.30  
  Purchase #2 $227.77   10.591%   $251.8931   $251.89   $251.90   $251.90  
  Purchase #3 $174.95   12.566%   $196.9342   $196.93   $196.95   $196.90  
  Purchase #4 $218.73   3.433%   $226.239   $226.24   $226.25   $226.20  
  Purchase #5 $182.78   13.231%   $206.9636   $206.96   $206.95   $207.00  
  Purchase #6 $89.96   4.798%   $94.2763   $94.28   $94.30   $94.30  
  Purchase #7 $196.96   11.234%   $219.0865   $219.09   $219.10   $219.10  
  7 purchase totals = $1,156.05       $1,264.7299   $1,264.73   $1,264.80   $1,264.70