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 $69.80   6.488%   $74.3286   $74.33   $74.35   $74.30  
  Purchase #2 $244.99   7.558%   $263.5063   $263.51   $263.50   $263.50  
  Purchase #3 $93.32   6.730%   $99.6004   $99.60   $99.60   $99.60  
  Purchase #4 $198.73   5.287%   $209.2369   $209.24   $209.25   $209.20  
  Purchase #5 $147.65   13.392%   $167.4233   $167.42   $167.40   $167.40  
  Purchase #6 $188.53   12.509%   $212.1132   $212.11   $212.10   $212.10  
  Purchase #7 $181.76   3.818%   $188.6996   $188.70   $188.70   $188.70  
  7 purchase totals = $1,124.78       $1,214.9083   $1,214.91   $1,214.90   $1,214.80