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 $198.62   6.770%   $212.0666   $212.07   $212.05   $212.10  
  Purchase #2 $233.33   13.816%   $265.5669   $265.57   $265.55   $265.60  
  Purchase #3 $119.47   10.285%   $131.7575   $131.76   $131.75   $131.80  
  Purchase #4 $96.70   13.224%   $109.4876   $109.49   $109.50   $109.50  
  Purchase #5 $125.67   10.632%   $139.0312   $139.03   $139.05   $139.00  
  Purchase #6 $147.49   4.269%   $153.7863   $153.79   $153.80   $153.80  
  Purchase #7 $93.95   13.221%   $106.3711   $106.37   $106.35   $106.40  
  7 purchase totals = $1,015.23       $1,118.0672   $1,118.08   $1,118.05   $1,118.20