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 $89.27   6.686%   $95.2386   $95.24   $95.25   $95.20  
  Purchase #2 $185.85   10.494%   $205.3531   $205.35   $205.35   $205.40  
  Purchase #3 $221.86   11.427%   $247.2119   $247.21   $247.20   $247.20  
  Purchase #4 $243.58   3.398%   $251.8568   $251.86   $251.85   $251.90  
  Purchase #5 $144.96   6.640%   $154.5853   $154.59   $154.60   $154.60  
  Purchase #6 $124.53   6.520%   $132.6494   $132.65   $132.65   $132.60  
  Purchase #7 $129.62   6.551%   $138.1114   $138.11   $138.10   $138.10  
  7 purchase totals = $1,139.67       $1,225.0065   $1,225.01   $1,225.00   $1,225.00