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 $191.40   3.460%   $198.0224   $198.02   $198.00   $198.00  
  Purchase #2 $246.33   4.543%   $257.5208   $257.52   $257.50   $257.50  
  Purchase #3 $56.60   7.227%   $60.6905   $60.69   $60.70   $60.70  
  Purchase #4 $7.44   7.435%   $7.9932   $7.99   $8.00   $8.00  
  Purchase #5 $224.41   3.838%   $233.0229   $233.02   $233.00   $233.00  
  Purchase #6 $5.25   7.670%   $5.6527   $5.65   $5.65   $5.70  
  Purchase #7 $243.55   7.593%   $262.0428   $262.04   $262.05   $262.00  
  7 purchase totals = $974.98       $1,024.9453   $1,024.93   $1,024.90   $1,024.90