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 $67.36   9.799%   $73.9606   $73.96   $73.95   $74.00  
  Purchase #2 $183.91   6.372%   $195.6287   $195.63   $195.65   $195.60  
  Purchase #3 $142.46   10.653%   $157.6363   $157.64   $157.65   $157.60  
  Purchase #4 $155.81   6.287%   $165.6058   $165.61   $165.60   $165.60  
  Purchase #5 $99.60   9.367%   $108.9295   $108.93   $108.95   $108.90  
  Purchase #6 $98.33   8.383%   $106.573   $106.57   $106.55   $106.60  
  Purchase #7 $219.80   3.423%   $227.3238   $227.32   $227.30   $227.30  
  7 purchase totals = $967.27       $1,035.6577   $1,035.66   $1,035.65   $1,035.60