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 $214.59   5.760%   $226.9504   $226.95   $226.95   $227.00  
  Purchase #2 $214.51   3.172%   $221.3143   $221.31   $221.30   $221.30  
  Purchase #3 $135.90   13.580%   $154.3552   $154.36   $154.35   $154.40  
  Purchase #4 $162.45   13.470%   $184.332   $184.33   $184.35   $184.30  
  Purchase #5 $115.29   9.869%   $126.668   $126.67   $126.65   $126.70  
  Purchase #6 $188.88   12.455%   $212.405   $212.41   $212.40   $212.40  
  Purchase #7 $154.55   11.522%   $172.3573   $172.36   $172.35   $172.40  
  7 purchase totals = $1,186.17       $1,298.3822   $1,298.39   $1,298.35   $1,298.50