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 $233.29   12.288%   $261.9567   $261.96   $261.95   $262.00  
  Purchase #2 $149.27   11.812%   $166.9018   $166.90   $166.90   $166.90  
  Purchase #3 $63.98   5.439%   $67.4599   $67.46   $67.45   $67.50  
  Purchase #4 $234.75   3.746%   $243.5437   $243.54   $243.55   $243.50  
  Purchase #5 $161.92   12.111%   $181.5301   $181.53   $181.55   $181.50  
  Purchase #6 $158.95   11.707%   $177.5583   $177.56   $177.55   $177.60  
  Purchase #7 $61.80   3.237%   $63.8005   $63.80   $63.80   $63.80  
  7 purchase totals = $1,063.96       $1,162.7510   $1,162.75   $1,162.75   $1,162.80