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 $174.73   7.266%   $187.4259   $187.43   $187.45   $187.40  
  Purchase #2 $23.45   13.779%   $26.6812   $26.68   $26.70   $26.70  
  Purchase #3 $231.33   7.435%   $248.5294   $248.53   $248.55   $248.50  
  Purchase #4 $147.37   7.563%   $158.5156   $158.52   $158.50   $158.50  
  Purchase #5 $93.37   5.282%   $98.3018   $98.30   $98.30   $98.30  
  Purchase #6 $247.43   5.464%   $260.9496   $260.95   $260.95   $260.90  
  Purchase #7 $56.95   6.765%   $60.8027   $60.80   $60.80   $60.80  
  7 purchase totals = $974.63       $1,041.2062   $1,041.21   $1,041.25   $1,041.10