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 $63.58   5.753%   $67.2378   $67.24   $67.25   $67.20  
  Purchase #2 $206.96   13.469%   $234.8354   $234.84   $234.85   $234.80  
  Purchase #3 $168.30   10.742%   $186.3788   $186.38   $186.40   $186.40  
  Purchase #4 $120.81   4.576%   $126.3383   $126.34   $126.35   $126.30  
  Purchase #5 $204.99   5.417%   $216.0943   $216.09   $216.10   $216.10  
  Purchase #6 $58.36   5.292%   $61.4484   $61.45   $61.45   $61.40  
  Purchase #7 $169.62   9.503%   $185.739   $185.74   $185.75   $185.70  
  7 purchase totals = $992.62       $1,078.0720   $1,078.08   $1,078.15   $1,077.90