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 $161.70   7.626%   $174.0312   $174.03   $174.05   $174.00  
  Purchase #2 $36.84   13.843%   $41.9398   $41.94   $41.95   $41.90  
  Purchase #3 $203.58   7.836%   $219.5325   $219.53   $219.55   $219.50  
  Purchase #4 $87.54   11.213%   $97.3559   $97.36   $97.35   $97.40  
  Purchase #5 $82.80   13.562%   $94.0293   $94.03   $94.05   $94.00  
  Purchase #6 $217.91   10.186%   $240.1063   $240.11   $240.10   $240.10  
  Purchase #7 $205.74   6.405%   $218.9176   $218.92   $218.90   $218.90  
  7 purchase totals = $996.11       $1,085.9126   $1,085.92   $1,085.95   $1,085.80