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 $181.69   8.542%   $197.21   $197.21   $197.20   $197.20  
  Purchase #2 $99.74   3.474%   $103.205   $103.21   $103.20   $103.20  
  Purchase #3 $185.97   6.242%   $197.5782   $197.58   $197.60   $197.60  
  Purchase #4 $166.98   6.524%   $177.8738   $177.87   $177.85   $177.90  
  Purchase #5 $246.64   3.227%   $254.5991   $254.60   $254.60   $254.60  
  Purchase #6 $59.59   8.512%   $64.6623   $64.66   $64.65   $64.70  
  Purchase #7 $21.63   6.485%   $23.0327   $23.03   $23.05   $23.00  
  7 purchase totals = $962.24       $1,018.1611   $1,018.16   $1,018.15   $1,018.20